Except then the Defenders would rule the crucible. Bubble train with 3-4 and feed 1 or 2 roaming supers and you could deny entire enemy team then harvest a nigh on full two wipes-possibly more if those roamers are Stormcallers-before restarting the train from those reapings. Enemy tries to counter oh no they made more orbs for your team to use and burned out their best answer, meanwhile you can finish burning them down after their animation. That tactic would be even more ridiculous for premades if bubbles completely nullified the supers needed to knock the walls down. At least now you got them to spend their super to kill you and prevented multikills, unless your team tries to pack more people into one bubble than is wise, it's also not like you have to stand inside it at all times, if you see a titan or warlock being ballsy enough to approach or a hunter pausing when they see you maybe you can back out of the bubble, use some other cover.