Dispel Flux can be game deciding early on but it obviously all depends on the deck you play and play against as well as the draws. As CT says, it is not entirely clear whether this makes it OP since other cards can also be game deciding early on (Ord Stone?).
I personally think it is the most boring card in the game. It completely encourages people to play rush decks and I think they are so unbelievably boring that I can't find the words for it. Pack loads of the cheapest creatures and a couple of cheap buildings and you have a competitive deck. Screw all cards that make for a fun game, let's see if your weenie is better than mine! Dispel Flux if someone disagrees!
But the again, and contrary to what many people on the forum seem to believe, cards are not OP because they are not fun to play with/against. That a card is not fun to play is surely not what makes a card OP; it is one possible consequence of it being OP. Thus, if I find Dispel Flux boring that really does not say anything about whether it is OP. Some people apparently thinks that it is a fun card
Hm... I am not sure what I am trying to say in this post... I just don't like the card and it makes for, in my view, a very boring TFW experience.