Reading some more comments let me rephrase this.
"Without nerfs they will player better to clear the instance"
No.. Without nerfs I will play better, to carry them THROUGH the instance.
"But it didn't kill me (with 15% buff) so I can just stand in it and have the healer keep me up through it"
"Oh it killed me I better move next time"
You're assuming they know what hit them.
No.. They are too busy staring at their actionbar clicking ice lance. When they die, it means they get to get another soda. Why would they check combat log, why would they try to figure out what they did wrong? Why would these people who can't even pass 1st grade mathmatics even think that their death was due to anything other then the healers fault? Or the tanks, provided they ARE the healer.
They will make NO attempt to move out of it next time. They will stand in the same thing. Five thousand more times... Algalon: "AND FEEL NOTHING" Metallica: "No remorse".
"Life is but a walking shadow, a poor herp, who derps across the stage, and then enters your heroics and wipes you for hours."
Am I getting through to you guys? This only helps the people who don't suck. Who survive the first shadow gale... And then are force to duo or solo down the boss. 15% more could be very helpful when three pugs just got gibbed by a whirlwind they stood in and you're down 2k dps because of it.