To Innociv, PossiblyImpossible and others who think alike : Do you mean that Oak, Sedna and Erebus are good as assassins only vs Unclean Beast, or are they ok vs the others too ?
If the latter, could you describe how that works ? For example, take Sedna vs any of these 3. How would you manage that ?
What I mean is that Sedna, QoT, Oak and to a lesser extent Erebus are all viable additions to a strong group playing as "Assassins," though they are rather support oriented. It's not that they are only effective against UB or themselves, but that they bring less to the table than the "Big 3."
If I'm playing a 3v3 in the game is it is right now, I have no doubt that the ideal team is Rook, Reg, and Ice TB. No doubt. If I'm playing a 4v4, the ideal fourth would probably be a healer Sedna or maybe QoT or Oak (with shields / ranged slows).
It's not that way because the Generals can't take on the Assassins one-on-one. They're actually not so bad at that. In a team game where players group together and take advantage of ranged snares, stuns, and high damage abilities coordinated together, then the Generals tend to be hold you back. It's more a balance issue with the "Big 3"Assassins than it is with the Generals, though, because the Generals do bring a good deal to the table, just not anything as obviously dominating in a team setting as the Big 3. The combo of snipe, auto-ranged-snare, 2-3x shatter combo, boulder roll, and hammer slam simply has no comparison. Plus, the Big 3 Assassins all have high weapon damage. Put all that together and they can incapacitate opponents for a long enough time to kill them, which is roughly 3-5 seconds. 
Unclean Beast is very strong, probably stronger than any of the Assassins, but he seems more geared towards dominating on his own, though he does have one channeled stun which is useful in teams.
I wouldn't feel at a disadvantage if one of my allies chose a General over UB, but I would feel at a disadvantage if my ally chose a General over one of the Big 3 (and the opponents had them).
