No, it wouldn’t. Tanks can do damage close enough to an actual DPS, the average player just hasn’t caught on yet. 25 mans would be even less affected. Having a tank respec to do 300 more DPS on a boss fight in a 25 man is virtually nothing.
Here’s an example of a 99 percentile Prot Warrior doing as much DPS as a 99 percentile Enhancement Shaman:
