Here's my feeling...I see two ways SD can do this...
1) Every faction is balanced, with having slight advantages in different areas
2) Each faction is balanced by having its own broken, OP strength
Now I personally prefer method 1....but if the devs prefer method 2, then honestly truce of rogues is pretty solid assuming that other factions have comparable advantages...
The biggest problem with balancing via method 2 is that early game OP elements are not consistently offset by late game OP elements...
Remember that one Advent faction is supposedly supposed to get free culture at each planet...so it wouldn't surprise me if the devs continue with the whole "balance by broken elements" philosophy....and really, that's probably the only way to get the factions to be truly diverse and unique...