I don't main warlock but I die far more frequently being close to my target than the walls of the room. Not saying this isn't a problem but definitely something you could work around pretty easy. As for whether it's skillful play to utilize the nova bomb and not die eh... this game is weird and sometimes you die for no reason. (Great example I was through an invasion portal in gambit and the invader on our side shot the portal after I went through and I died) That's kinda just video games because of all the variables that go into coding different abilities and terrain. My personal opinion on this just don't take a death, wipe, or game in general seriously it's more fun that way.