Yes, there is a limit in place for mana value 3 or less, but if youre already caring a lot about your mana curve and the amount of mana you spend on spells, chances are you will have plenty of targets for this card
Whenever equipped creature attacks, you may put the top two cards of your library into your graveyard
Zhao, Ruthless Admiral is a flexible creature that can go into the red-black deck, and is especially synergistic alongside permanents that can sacrifice themselves like Clue tokens
I am betting it will be an auto-include in a future Deckbuilder's Toolkit
The implied plan is clear, include a bunch of blight cards in your deck that put counters on your cards, and then gradually burn the opponent down with tarfire damage turn by turn
Aetherflux Reservoir - if your spells are nearly free, this becomes your win button