Counterspells get more and more complicated with each new MtG set. Whirlwind Denial not only counters spells but also triggers abilities that those spells might be possessing.
For example, if your opponent plays Hydroid Krasis, then you can easily counter it and all of its triggered abilities. It is well known that even if you counter Hydroid Krasis, it will still draw cards. But not if you use Whirlwind Denial — unless your opponent has some way of paying four mana for each trigger.
Even if this card won't see play in main decks, it will definitely become an excellent sideboard counterspell.