The arena buff looks a bit extreme. It really means new players that don't want to spend on upgrades are pretty much shut out of Mid-High level arena forever. Even a 20% buff across the board is often enough to completely dominate a team.
Course this won't matter if HB gets distributed correctly by then. Probably won't though.
Regardless, if it does go live, thankfully it is relatively cheap to inflate ones Might instantly (as compared to getting 5/5 revite talents, etc.). The real question is if its worth holding on the Legendaries now in anticipation for this. Ole Hanyabull says, "Eff that!"