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Im going to say its pretty useless, unless you are lucky enough to time your fight with your level up, and its too infrequent to be of any other use.
Hehe...I just described the perfect use of this.
The beetle cavern is great for toons lvl 70-90 to get anywhere from 200k-400k xp in 20 min. Just do some Musty quests or grind like usual. But when you're somewhat near levelling, head on over to the beetle cave (assuming you've done the quests that lead up to this).
The point of the beetle cave is that it's non stop spawns of the lvl 80 beetles that go down quick. Don't mess with the nests and they will spawn constantly. A commando, bh, or medic tears that place up. Just use AOE DoT attacks and finish off with your other attacks.
PLUS, if you use this trick that the OP posted, you'll notice that you won't take hardly any damage and can pretty much spam all the specials you want in the middle of the cave.