Cruiser work pretty well, I think. In damage and in tanking. I'm an engineering captain and yesterday I fought in Ker'rat as red-Fed in my Galaxy against a Defiant, two Galaxies and admiral(!) in D'Kora. I tanked them all and killed them all. Ok, they were lousy PvPers, but still - 1 vs 4, among them an escort (pretty good one, had to be killed first) and still won. In a cruiser.
I also got 1v1 against P2W ships - Tactical Excelsior (also captain) and never felt that I was underpowered compared to C-Store (so P2W) ship. Some Klinks intervened but had they not I would be able to hold off him and, if I had enough luck - kill him to. Or die - it was even fight. Still: free ship vs P2W one can be a fair fight.
In the end it all comes to the captain skill. I'm not some super-PvPer, I got my ass handed to me often enough, but I'm also good enough to win against some good players in ships that are P2W and/or support my team if I have one.
Escorts pack a lot of peak damage, but are susceptible to damage over time. You just need enough patience to outlast them. Don't kow how it will look against Jem'Hadar bug or Fleet escorts - never fought them, but I doubt it will be all that different.
i think they are all scaled to your level in kerrat, or you are to theirs. Or maybe that excelsior was the commander version...hardly a p2w ship.
and yes...en engi in a galaxy that killed off 4 others...they must have been real bad PVP players. You are in for a surprise once you hit max lvl and enter kerrat.
i guess you are above average, just as me when it comes to PVP. And i had the same experiance when i leveled my last toon and entered some PVP matches. 80% of the matches i made all the kills or 13 to 14. And i didn't lose a single FED vs FED...only 2 or 3 arenas against klingons i lost.
I know for a fact that many of those players are not even new to the game...there are just generally very unskilled players out there.
and as you said...it depends on the captain, since there are cruisers out there that can do some impressive damage while tanking anything, but still within the boundrys of a cruiser. Imagine those captains gaining access to even more firepower. would make other ships obsolete.