I thought of exactly the same thing about 5 days ago. It prompted me to do some math and surprisingly the Helstrum combo is not as good as it looks. You loose out on the best defense he can get, VHS and AoMI. This makes him really, really hard to kill with his 4+ ward on top of that. Anyway, here is a brief mini-article I wrote a while back on warseer. I have been meaning to edit it with some of my new experiences, maybe in a day or so.
Anyway, on to a brief tactica about this bad boy. . .
Either way it is a great unit. As has been said before its "only" 100 pts for a 5 wound chariot with T5 and a 4+ ward save. Thats incredibly cheap. The only drawback is that you have to put your general on it (unless its a 3k game).
Equipping the Arch Lector:
There are a few main ways I see to equip the Lector on a war alter; many are expensive though.
Cheap:
Heavy Armor, Enchanted Shield, Sword of Might (261 pts). This option gives you two S5 attacks and a 3+ save in combat (1+ against shooting). Of course the magic items could be dropped totally to save 27 pts but then you only get a 4+ save and S4 attacks, pretty sad for your general I think. Swap the Hvy armor and Eshield for Armor or Meteoric Iron for only 4 extra pts to get a better save in combat.
Defensive:
Dawn Armor, Shield, Sword of Might, VHS (308 pts). With a 3+ rerollable save in combat (1+ shooting) and the ability to swap stats in a challenge this guy is pretty survivable, especially since he can heal wounds up to two times (once with a prayer and once with the alter). Also consider adding the Jade Amulet to shrug off the first wound (cannonball anyone?) instead of the VHS or Dawn Armor for an extra 10/5 pts. I dont think its worth it, but it is fluffy.
Monster Killer:
Heavy Armor, Mace of Helstrum, Enchanted Shield (306 pts). Taking one S10 attack instead of 2 S4 is a great tradeoff, especially since he has hatred and the ability to reroll hits and wounds with the casting of a prayer. Against monsters d6 wounds is great especially when you have the impact hits at S5 going for your same target. For character killing consider swapping the Enchanted Shield for the VHS for a higher weapon skill and to lower your opponents stats, however most of the benefits are lost with the mace. I wouldnt do it as it costs and extra 18 pts (buy a mundane shield) and your save becomes a lousy 4+. The Speculum is there to make your enemies S6 with a GW instead of the chariot popping S7. Cool use of it and I would definatly consider doing that in a very S7 heavy environment (lots of lizzies, chaos, vampires). Against a tricked out lord with a 1+ save and 4+ ward you only have a 30% chance to wound him (that means only a 20% chance to kill with 3 wounds -- but most other combos cant kill a lord outright like that).
Character Killer:
Armor of Meteoric Iron, Sword of Might, VHS (295 pts) this gives you a solid offensive character with a 1+ save and stat swapping +1 S attacks for 'only' 295 pts. Will do about 1 wound to a 1+ save 4+ ward S5 T5 Atk 5 character per round. You also get steed attacks (shouldnt do much) and impacts hitting the regiment. The real benefit is that your enemy now has 2 chops hitting on 4s and wounding on 3s (assume S6 with GW) and must get past your 4+ armor and 4+ ward saves.
Armor of Meteoric Iron, Hammer of Judgement, VHS (305 pts). IMO this is the best offensive combo as swapping T gives your opponenet a 1/3 chance per hit of being wounded with no save (thank you T4 Speculum Swap and Hammer of Judgement). This really shines against hardcore chaos lords and vampires. Against unit champs you might as well take the sword of might because its cheaper (although the hammer is still better).
I have been using the cheap option to great effect lately. If I played games over 2,000 pts I would try out some other kits (VHS, AoMI, and Hammer is my second favorite), but simple and cheap means more bodies on the table.
Deployment Strategies:
Since the Alter is a large target you obviously want to try and protect it against armies that have a lot of S7 shooting. Shots at less that S7 are not that scary as the alter is T5 with 5 wound and a 4+ ward and the Lector has 3 T4 wounds with (hopefully) a 1+ armor save and 4+ ward. Even so, the prayers do not require line of sight and the only light spell to need LoS is the first magic missile. I like to hide him behind some terrain so its out of sight for the first turn or so. The I try and maneuver him around that piece of terrain so only half (or less) of enemy shooting can target him.
Placing him central is a good idea, since LD9 is really good. However, if you place greatswords on the flank and have the lector on the other flank, you should be able to give your LD to all units besides the swords. This places your alter in a great position (as with US6 you want to flank) and still confers your LD bubble to many weaker units.
Movement and Combat:
Like I said earlier, hide the bugger as much as you can against shooting in the first 1-2 turns. I am not saying to be overly cautious, as he can take a lot of punishment before he goes down. Play smart and only hide from real threats (two cannons on a hill) and go all out towards the smaller threats (bowmen, ha). Try and flank where you can, but unlike a griffon count you are unbreakable. If you need to charge into combat to be protected from shooting or to pin an enemy unit down then do it. Charge a scary unit (as long as they dont have S7) and watch them sit there. Then flank them next turn with some nilla knights or a parent unit.
You want to be in combat with the lector. Sitting around he doesnt do much. In combat you get 2 WS3 S3 and 2 WS4 S5 hatred attacks that probably reroll wounds (assuming sword of might or GW) plus d6 S5 impact hits. This is all after you cast soulfire to get d6 S4 no save hits and Cleansing Flare to get d6 S5 hits on every enemy within 12". Not bad if you ask me. So you kill 6-7 enemies, lose combat, stick around, flank, kill another 10, pursue. Dont forget that you can still charge 14". Hang back from your line and go barreling in on turn two or three.
Remember that you have to pursue because of hatred, so be careful of where that might take you. Also be aware that enemies will often flee from this awesome unit so keep in mind where the 7" move would place you.
Cons: This thing isnt perfect. You can still be popped by S7 and you are a large target. Your lector only has a base 2 attacks so the only way to beef him up is with expensive magic kits. I consider him a more survivable Griffon Count and I think he should be played like that. WarhammerEmpire.com has a really good griffon tactica that would help a lot in learning how to play the alter. Remember though, you dont cause terror like a griffon, which means you want to get into combat much quicker so you can actually do something.
Good luck with the Alter, its by far my new favorite unit for not only fluff reasons but gameplay reasons. Plus the conversion opportunities are amazing.
Thanks for Reading,
Tom