know how long it takes for enemies to kill you and how long it will take you to kill them before you jump into battle with them. meaning if you can't kill them all before needing to take cover then you have to adjust your strategy.
always be moving side to side and jumping to avoid enemy fire.
get yourself some good weapons, if your having trouble get an unkept harold and a slagga. the slagga doesn't matter what level it is, the harold you can farm the bar room brawl until you get enough tokens in TVHM and then buy it in UVHM at your level.