There's a bug or something in thaumcraft
Focus gaining tool effects when that tool holded in right hand (never tryed left, but any way)
And that's kinda OP sometimes... But interesting

Why anyone should fix this, while you can make feature of this

If I would balance this, I would make it damage tools on focus use
And even damage 2 or 3 times faster

Then... Is there need for special researches?
Maybe a knife for less tool damage
Or even an infusion for tool to make it more durable to damage from focus "synergy"...

P.S.
Long time no see)

The problem with making that mechanic have a cost (durability or otherwise) is that the normal TC gauntlet would still be free. Normally having upgrades not just be better in every way can be good thing, but in this case it wouldn't fit the lore that the TC gauntlet was not that great (due to using iron and such instead of better materials).

So... Is there any kind of "Cast event"? If so, then there's no need to edit any gloves. Every "cast event" will damage main hand tool/weapon.
Or, well
Firstly
Someone needs to fix that bug to make TC gauntlet do not use enchanting effects...

The problem with making that mechanic have a cost (durability or otherwise) is that the normal TC gauntlet would still be free. Normally having upgrades not just be better in every way can be good thing, but in this case it wouldn't fit the lore that the TC gauntlet was not that great (due to using iron and such instead of better materials).