The Tanker has no ability to take advantage of the increased cap on its own. Even double-stacked Rage, 95% damage enhancement, and Musculature Core Paragon is still below the 400% damage cap they have currently. It won't make a difference outside of extreme team buff situations.
Punchvoke doesn't even kick in until level 10, at which point you can have Taunt and will have had plenty of opportunities to have taken both your T1 and T2 attacks, and I don't see why you wouldn't with Ice Melee, since it loses an attack to get Ice Patch. I really don't think the swap is a bad thing for Ice Melee.