So, you want to buff mummy because the buff wouldn't hinder it? That's not a very good reason because a buff, by definition, makes a card stronger. In order to have my support, you'll need to provide a reason why the card is UP, and I don't think there is one, because it is a better attacker than the blue crawler, graviton merc, and flesh spider.
Also, keep in mind it's ability makes it slightly stronger, not weaker. It's semi-immune to RT. While your creature loses 2 attack, the player with the mummy does not lose a draw. The extra draw can help them get more damage or defense: