Could we buff Piercing Thoughts for Mages?

I usually only go for Deathfire Touch on a mage when I want the additional 7% magic penetration from Piercing Thoughts to help deal with MR stacking tanks and / or bruisers, as the DOT effect from DFT isn't really that noticeable until mid-late game. (I am fine with Deathfire Touch as it is). However, %pen stacks multiplicatively. When combined with Void Staff, this mastery only gives a ~5% increase. 'But why buff Piercing Thoughts?', you ask.

Well, mages have 2 legendary magic pen items + boots

at their disposal, while there are 12 legendary magic resist items + boots (did I forget one?).

,

Oh, and I am forgetting Windspeaker's Blessing, the Resolve Tree, and magic resist glyphs / quints / etc.

Seems fair. So pwetty please could we buff the %pen from Piercing Thoughts to 10, 12 or 15%? Or...something? Thanks.