Deepspace Encounters. I can sit there at the enemy's spawn points and leave for a while and I'll obliterate everything - sometimes four Klingon capital ships and a few support ships - I can even hold my own against the Romulan flagship and its supports and sometimes even the Scimitar and my shields won't even budge (on the Klingon ones) but when I face down a few birds of prey in P2P or on a mission, I'm toast.

Unlike most content, Deepspace encounters do not scale to your level, that's why you can crush them so easily. Try the encounters in the new sector, they are max level.

I like the Deep Space Encounters not level matching, it means I can take my defiant with only quad cannons equiped and fly around like a lunatic blowing space ships up.

BATTLE!

I love that!

This. You have to look at what level the NPC ships are at. . .even then, some scenarios have innately tougher ships (such as No-win, STFs, etc).