you seem to have this thing in your head that trusts replace partys fully, at no point were they ment to replace partys fully, they are ment to assist in standard stuff that currently is lacking, most endgame that can use trusts are mostly T1-3 depending on zone and which trusts, everything else pretty much means the trust will die fast or just can't hit the target.
Yes there are some trusts that work better than others however it still doesn't replace real players for higher endgame content, that being said, if you havn't obtained it, then try playing the game instead of not playing it,or do the relivent fights such as SR to get em.
Whats that? you can't solo SR because you trusts aren't enough because they are too weak or too dumb? considering SR is endgame i am not suprised, only those who are generally pimped can solo using trusts in such a way that they just assist minorly rather than fill the shoes of partys in endgame