Horrors of Tzeentch absolutely sucked. A Firewyrm with ST6 and ball&chain can do massive damage, yes, but it has 4 move, and for every move, there's a 1/6 chance of failing, and causing a turn over. The pro means that it's more like... 1/12 chance on every move, but with two fireworms, you have to hope for 1/12 eight times before you can even start using the rest of the team, which is the part that's supposed to do stuff.
Bomb wasn't reliable at all, you could use it with the wyrms at short range and hope, but the Flamers only have AG3, and even a quick pass is hard to make for them. Throw team mate isn't reliable enough to make these guys good either. I'd much prefer a treeman or lots of move or whatever.