I'd like to make a couple more suggestions - which do make sense to me atm - and hear your input on this.
1- Instead of focusing on making a change to the Teleport card itself, why not leave it exactly as it is ... BUT ... instead
change Nullify to become NON-MANDATORY. ( just change the "must" to "may" )
Instead of having to spend your Nullify on the first Incantation/Enchantment thrown your way, let the Nullify controlling player decide if he wants to spend his Nullify or suffer the spell's result.
This way Nullify would become more like a "counterspell" in Magic : having the potential to counter a spell but at the same time having to decide when and what exactly you're going to counter/nullify.
Sure, Nullify would get "better" with this change but certainly without becoming overpowered imo.
You can still only stop 1 spell per Nullify, but you get more control over what you counter and this could possibly be just the right medicine to tone down Teleport.
And after all .... there's still Seeking Dispel in case you want to remove a face down enchantment on the opposing Mage.
2- the second suggestion I'd like to make expands on the previous suggestion :
allow players to play multiple copies of NON-mandatory face down enchantments on an object.
atm I don't see how this could be broken ( but maybe I'm missing something and that's why I'd like to hear your input )
So what's the problem if your opponent wants to play a back-up, face down, Bear Strength on his creature ?
If I end up not destroying the first Bear Strength he's just wasted 2 mana and a Quick Action on a card that will not see play.
However, having two (non-mandatory) Nullify's in place could actually secure you of not being able to be messed with at all in a given turn ( read : teleported ). However, you've still invested two actions and 4 mana in it beforehand without knowing if you'll actually need them, making this quite balanced IMO.