I guess the ability to flash this in on your opponent's end step, kill a blocker, and then hopefully defeat the battle could be powerful, although this still requires dealing five damage to remove the defense counters
On top of that, it reads: Whenever one or more Dragons you control attack, draw that many cards, then you may put a permanent card from your hand onto the battlefield. Everyone likes free stuff, and that free stuff is even better if its a 15-mana Earthquake Dragon
FromTheShire: Absolutely LOVE the villainous choice mechanic, and Davros forces a great choice for you
White Plume Adventurer was eventually banned in Legacy, while many of the common initiative cards like Aarakocra Sneak and Vicious Battlerager were banned in Pauper
A hasty 7/5 that cant be blocked by chump tokens or utility dorks is threatening, especially because the cost of trying to get rid of it is losing an artifact or creature