I want to believe this is decent. It is obviously only great if you have surge active, but in the proper lists that can be trivial, and 2 mana counters have been seeing less and less play, but it is an uncounterable counter at 2 mana, which seems like it would be very game winning when relevant.
Mana Drain is fringe right now, and this would fit into a totally different archetype I think, but this can be an absolute answer to protecting your mentors or Salvagers, or very definitive way to push though your game winner? Maybe more sideboard against control matchup where you know you will be trading spells?
For creatures I'd rather use Caverns. For other spells - This doesn't protect your stuff any better than any other counterspell.
I cast say Tinker.
You FoW it.
I over whelming denial your FoW. You let it resolve then
You FoW or REB my tinker. Or in this case we see how strong Overwhelming denial can be and you Overwhelming denial the tinker.
It doesn't push thru game winners. Its defensive and stops them.

Good potential. I think we'll see it pop up in some big blue style decks.