The front side isn't bad, and it coudl do some serious damage to token decks that aren't buffing their creatures with counters or anthems
Number 866 Language English Legal Formats Brawl, Commander, Competitive Brawl, Historic, Legacy, Modern, Pioneer, Timeless, Vintage Not Legal Formats Alchemy, Pauper, Standard Rulings (5/3/2019) The power of the Zombie token is checked only immediately after it attacks
This is extremely rare and never guaranteed.
Fortunately, you can also sacrifice your own creatures, should they bear egg counters
So while Addle rarely misses it still doesn't hit the most relevant target as often as you need for a two mana card of this nature to be a big deal
For regular price, at least