The Shamblers are the latest (and fourth) unit available to the Blindwater Pact. It consists of a Gatorman Bokor wielding some sweet voodoo magics, and (beginning with) 10 really crappy zombie Trogs under his command. This unit would probably be 3pt in Cryx, it is twice that much for us Gatormans. Minion tax and all that.
Damage
The Shamblers themselves are MAT 5, P+S 8 - not that impressive. They do have CMA however if you buff them up with Fury then they can get a nice damage output, effectively hitting at MAT 7, P+S 13.... the same as a Gatorman.... without reach or rerolls.The Bokor with his Death Magic rule is the star here however. Death Magic allows the Bokor to RFP a Shambler in his CMD range to boost an attack roll, boost a damage roll or buy an extra attack. Therefore if you somehow get 20 Shamblers on the board, this guy can get 7 fully boosted POW 12s by just walking into combat with the target. If the target is a warcaster with average ARM, that target is dead. If the target is a light warjack or warbeast, that target is dead. If the target is a warlock, that target is most likely dead. Basically, necromantic sacrifice magic means big damage output potential - but it is situational and largely nonthreatening to ARM 19+ models in true Gatorman fashion (excluding Fury, of course).
Survivability
On the surface, this unit looks as squishy as Bile Thralls - 10/13 dies to almost anything. The Bokor has a standard Posse defensive statline so is a little tougher.However, the key to this unit's survivability, and its ability to tarpit, is the Bokor's Raise Dead and Death Magic rules. The former grants the Bokor a corpse token for each living model that dies within 8", and each corpse token becomes a fresh (or not so fresh, as the case may be) Shambler during your next control phase. The latter rule allows the Bokor to shunt off damage he suffers to Shamblers in his CMD range, at the rate of 1 damage point per Shambler.
What is really stupid about this rule, is that if you make the unit tough, it essentially gives you a tough save against every damage point the Bokor suffers, since the damage shunted occurs before the disabled -> boxed -> destroyed step. Bring those Witch Doctors along - even if the unit gets nothing from Undead, it gets a LOT from Tough (as I have always said, making 10-man units tough is stupid).
In summary, the Bokor is respectably hard to get rid off, whereas the Shamblers themselves die in droves. It's good you can make more to replace them though, which allows them to tarpit well against lists that lack ranged removal (ie. Cryx, Gators, most Skorne)
Utility
Besides their ability to recycle dead enemy and friendly models (primarily friendly - I have learned that there is quite a practical difference between the Bokor's CMD 8 and Alexia's CMD 9) and act as a tarpit somewhat comparable to Gatorman Posse against the right target (ie. small-based weapon masters), the Gatorman Bokor also has Hand of Glory, a RNG 3 stationary-causing magic attack. Given that Death Magic also allows the Bokor to boost attack rolls, this can be a pretty sweet ability. However, one must keep in mind that it is still a magic attack and it can be shut down by anti-spell mechanics like Banishing Ward or Bestial. Furthermore, it suffers the penalty for spellslinging into melee and walls and all that jazz if you don't get in combat with your target (which if you do, you may also want to consider just killing it by Death Magicking all your Shamblers). Basically, the ability is sweet but much less sweet than it initially appears.But it can be a nice boost for warbeasts to not have to roll to hit other DEF 12+ warbeasts or warjacks. It is also pretty sweet if you make a warjack stationary and beat up on it a bit, then follow up with a Thrullg disruption so it cannot shake.
Tactica
First of all, make no mistake - this is a straight up worse, non-character version of Alexia and the Risen for 1 more point. Now that we've cleared that up.....
EDIT 2015: If I were to summarize primary Shambler strategy in one line, it would be: Gatorman Bokor and Bog Trog Shamblers.
The Bokor is basically a super solo that can boost a lot thanks to his disposable Shamblers. You keep him back for late game, gathering corpses as you go and occassionally throwing out a few Shamblers. When you have a nice glut of corpses and some savoury charge targets, you charge in with the unit, make all the Shambler attacks and then sacrifice the majority of the Trogs killing a fresh heavy or something. Shamblers as a frontline unit is probably only worth it against a wave of fast weapon-master infantry that can alpha your Gators, or to jam up things on a flank somewhere. Otherwise they'll just get in the way.
In terms of support spells, Iron Flesh or Death Pact will not do a lot for the unit since their stats are terrible and they are already undead. Save those for nearly any other model in your list. Fury however, is pretty baller since CMAs now become MAT 7 POW 13s (just like Posse!!!) and the Bokor becomes P+S 15, which means he can really blow shit up with his boosts and additional attacks.
For warcasters, these do pretty well with Rask (who doesn't) as they provide him with an excellent and cost efficient ablative shield of Call of Sacrifice targets, who despite not hitting as hard as Ambushers late game, can still do some respectable work. They benefit from Fury well.
Barnabas can protect them with Swamp Pits, or else they will get shot by any guns. Those weeny POW 10 shots that your Posse mostly laugh off will completely shred these guys. They also provide a cheap tarpit to help you on scenario, and some reasonable damage output from the Bokor in case you really need it.
Likewise, giving them Stealth (with Calaban) will allow them to run across the field to jam and do their part.Whether you give stealth to these guys or you other models depends on the strength of shooting/spells on the other side of the field - if it's all POW 10s, stealth the Shamblers since they get shredded by POW 10s and the rest of your force doesn't care. If it's mostly higher POW, boostable guns, stealth your beasts, Calaban or Posse and let the Shambler eat the shots (or just play Rask and deliver it all intact).
Maelok can buff them a little with his feat but otherwise would probably rather just have more Posse, beasts or solos than these dudes. The few times I've played them with Maelok I haven't really gotten much out of them, and they tend to just trip over themselves. This of course could just be down to my inexperience with small-based infantry. Furthermore, Maelok usually likes having his Posse Undead for a really strong feat turn so you're unlikely to be getting corpse tokens from them.
Having said that, the Shamblers have good synergy with the Witch Doctor. Sure, granting them Undead is almost entirely redundant (afters one model - they are a living and undead unit!), but making 10+man units tough can really be quite ballbusting. Additionally, their ARM is respectable enough to be used as Sacrificial Strike fodder since, unlike Gatormans, their unlives are almost entirely worthless.
Summary
On the whole, I believe Shamblers are a nice unit to have but don't provide enough different playstyle options to justify taking them over more Gatorman Posse or warbeasts most of the time. I believe they will prove to be more worthwhile in Skorne where they can get the +2 STR/No KD tough all the time in combination with a lot of sweet Skorne buffs like Last Stand or Fury. They could probably also do some cool stuff in Trolls, playing as the second wave behind a wall of living Trolls and keeping the Bokur hidden behind a wall of rocks, or in Circle for the 'Morvahna Regrows Bloodtrackers -> Bloodtracker dies -> Bokur gets a corpse token -> Bloodtracker comes back next turn -> repeat -> trololol' trick.
Also if, like me, one of the main reasons you play Gatormans is because you dislike 10man small-based infantry units, this unit is like an uppercut to the nuts.