So for the tower, just go there at any given time pretty much and wait a little. Should end up with 5 or so people after a bit, someone will start it and just do your best to contribute. It shouldn't take more than a couple tries that way to get it done most of the time. For other pve activities like the bunker and legendary zones you can bull your way through, might need a smidge of gaining power but not too bad. See with those nothing really resets after death, so you can grab a few random weapons and rush in, kill what you can, rinse and repeat. For the legendary today for example I grabbed a couple shotguns and a sword to clear the first two rooms with their champions. Then swapped to a solar submachine gun, sniper rifle, and solar machine gun (though most any solar heavy woulda worked fine). Blasted my way to the upper platform so I'd be out of the way of the champions, then popped out on the ramp to burn away the boss's shield, pop him a few times with the sniper rifle. Rinse repeat until dead, he runs up the ramp at the end but by then you can usually burn him down and use a finisher, or pop super. Then open the boxes. For the bunker I generally have been grabbing an anti-barrier submachine gun, and overload autorifle, and then power weapon of choice. Then just play as normal using the right weapon on the right champion, and if I die just keep going since death doesn't matter here.