He's placing his AoE. That's not a hack or anything. Clever use of game mechanics.
Except for the fact that there's no recourse to prevent this. Picture this situation - you get past the 2nd doors in 2 minutes, are are onto the 3rd, but 2 sorc/sages use /stuck on the defending team so they respawn beyond the barrier at the 3rd spawn location. Those 2 players can now prevent you from ever progessing to the 3rd door area for the next 5min 30sec of the match without you having any way to interupt them, CC them, attack them or stop their actions.
That's an exploit. Argue against it if you'd like, but what i just presented is reality - it creates a situation that cannot be countered by the attacking team, and will stop the attack dead in it's tracks 100% of the time. Then again, using group stealth on an already stealthed player so they can stealth cap is also a "clever use of game mechanics", but you can't do that anymore because Bioware deemed it an exploit.
I'm curious about why you're defending this obviously broken mechanic?