Bolt,
MC's, Soul grinders, fiend's/daemonette's/seeker's with rending, and thats about it for anti tank. Welcome to daemons
Popular Tzeentch units are
MSU bolt horrors- 5xhorrors with 1 bolt and of course 1 unit with changeling because he is a bargin for 5p. Use 4+ of them. Also Bolt princes- a common cheap and cheerful bolt prince is
MoT, bolt, gaze. 150/155 (cannot recall off the top of my head), and he might be footbound, but has a 4++ and can shoot 1 S8 AP1 shot and 3 S5 AP3 shots each turn, AND can smack heads together in
CC as a monstrous creature. Also bolt heralds on chariots- they are very cheap, you can take 4 of them, good
BS, throws out bolts/gazes, has a 4++ as well but doesn't smack heads together in
CC as it is not a
MC. Spits out bolts and is a very good buy, considering the number of mobile 4++ wounds you purchase.
Although, I will throw this out here and probably be branded a heretic, but choose carefully if you want plague bearers. They are not plague marines! They are supposedly our best objective holders, with their
FNP and T5, the idea being that you sit on an objective in cover and camp it.
The problem is- you paid for a bunch of bodies in an army that is light on them to do
nothing. Plague bearers are terrible, terrible in
CC. That objective can be contested by grots practically. If a tank rides up to contest, your plaguebearers are going to moan and groan and scratch the paint and do nothing. It's literally forcing your opponent to contest and objective or you get it. And as a big fan of contesting my opponents objectives with empty transports and speeders, I gotta say it ain't that hard. This unit is also not shooting. I could be making my opponent come after that objective with a group of horrors that are worse in
CC (not by much ><

but can actually shoot and a 4++ is one of the best saves we've got- that it is a invul helps. The last thing it when the objectives are not in cover, and i mean area terrain- a wall can be walked around and your unit is no longer in cover, and when they are eating dirt like plague bearers are it makes it alot easier, area terrain not so. I might place a objective in cover, but my meched up friend doesn't fear my lack of shooting- my opponents would routinely NOT place their objectives in cover. When you're not in cover, your 5++ and
FNP isn't the same as 3+ cover and
FNP. It's miles, MILES away from 3+ armor,
FNP, T4(5), boltguns, pistols &
CCW's, and pair of special weapons and possibly a fist that plague marines get. Not to mention the rhino you gotta blow first. Plague bearers ain't got

on plague marines. Think carefully before you buy 20 plague bearers!
On a side note...anyone wanna buy 20 plague bearers off me

?