My favourite psyker power from the PnP line (especially in Dark Heresy) was the ability to dominate the enemy - with a success on an opposed Willpower test (which in general should be fairly easy for any psyker, as Willpower is supposed to be their main stat, while other classes/NPCs generally neglect it) you could force enemies to even harm themselves (IIRC they had some WP bonus in that case, but usually still manageable for good psyker builds), people in my group that played psykers spent a lot of time forcing enemies to pull the pins from the grenades they carried and such. Plenty of fun was had.
RT's Astropaths are more limited and not as OP (which follows lore), but they have a crucial advantage ported from that book forward: They can choose to limit themselves to not cause Warp fuckery, or even replace the result on the table with one you want (most of the time).
Yes and not just that, PnP Rogue Trader was pretty ground-breaking release in the FFG 40K line as it ushered in quite a few much needed changes from the original Dark Heresy rules. The other big change that RT brought together with fettered psychic powers was the variable las gun settings - in the original Dark Heresy rules las weapons were clearly inferior to solid projectile weapons - SP weapons could be silenced, use special ammo and use all three firing modes (single, burst, full-auto). On the other hand, las weapons could be only fired in single shots or bursts and their only advantage was higher reliability (which wasn’t a big deal anyway, if you used at least average quality SP weapons). The variable las gun settings (basically an ability to increase ammo consumption for increased damage and penetration) finally made las weapons competitive (though I would still argue that SP weapons were better overall).
I don’t have the RT rulebook on me right now, but I think that RT also introduced the change of rules for full-auto fire (maybe that came with Only War though, not sure now), which also made the ranged combat more balanced (original DH rules gave +20 to Ballistic Skill for full-auto fire, so people were mostly just mag dumping all the time, later it got changed in favour of higher accuracy for single shots).
We actually used to play Dark Heresy with these rule changes from RT ported back to the original rules - it made the game better.
[Steve gets a Kidney but I don't even get a tag.]
