It depends on group make up. I'm not sure how happy you'd all be if every boss fight devolved into hitting with the daily, then standing 15+ squares away and pelting it with longbows til it died
I don't know what could posses them to think giving a huge effect with no save and unlimited duration could be a good thing. The power would allow a rogue and a ranger to kill a lot of things many levels beyond what they should be able to if they can land this power.
And if the DM has to go over a module and redo everything just because of a single power... it's busted.