Any bomber that isn't protected or flies into overwhelming force is going to have problems, B-17's, B-24's, and Lancasters included (as I can tell you from much direct experience in scenarios).
Take Ju 88's, TBM's, and B5N's as examples. None of those are nearly as good as the Ki-67 in survivability. The Ki-67 is much faster and has better defensive guns. Also, the TBM and B5N don't even have formations. Yet I've flown in scenario missions where I had an excellent time fighting my way to target along with enough escorts that I didn't die, plastered the target, and got back home.
I've also flown in scenario missions in B-17's at 25k among 30 other B-17's with escort and not made it to target because we just got overwhelmed.
It's not the bomber, but the situation. The Ki-67 is an excellent bomber.
Here is a pictorial where I, alone in my formation of Ki-67's, got attacked by two F4U-4's and survived to tell the tale:
http://www.electraforge.com/brooke/flightsims/scenarios/200607_downfall/frame2_pictorial.html