Quote: (The_Real_Chris @ 03 Jun. 2009, 21:33 )
I think the 4 strong formation is based on there being some fluff on 4 per company.
That's a very liberal estimation; I'd hazard a guess that it's more like 2-3 on average. Ultramarines chapter roster in Codex: Space Marines 5th edition gives a total of 26 in the chapter, and only 3 companies have 4 or more (Emperor alone knows how 9th company got their paws on 7 of them). Of course, part of Ultramarines' armory was destroyed in the Tyranid Wars, but most of their Dreadnoughts were probably repaired in the time since, and they were likely to have quite a few of them compared to less illustrious chapters.
Dreadnoughts are also very permanently assigned to particular companies - even when the guy inside croaks, the shell isn't reshuffled back into Chapter reserve, but instead given to another one from the same Company. That also makes larger formations harder to arrange, compared to stuff like tanks that come from a single pool.
BL - that's kind of a moot point as you can already fit 2 dreadnoughts in a T-hawk in Epic:A, and it fits 40 guys, not 30.