After playing with this for a little bit, I've found a few issues...
in arena, there are several ways it gets knocked around, fire shield isn't one of them if you get enough scarabs out as they keep getting bigger (and 8 hp Pharaohs is enough to keep them alive for a while). Lobos hurt though...especially if they get out quicker then you get out a pharaoh. If they get out a lobo first, dropping 2-3 pharaoh might help if you don't just scrap the game anyway.
with 30 cards, 3 hourglasses was plenty, and without an eternity, I found myself decking out too quickly to storm the opponent (remember, arena, up to 200+ hp).
Another weakness is the lack of gravity, I was running out against wennie decks or the critters were too big to eat to begin with. if you get enough scarabs out before they wear you down, it's not bad as they boost their HP on their own.
There were a few other decks that I auto-quit against, other then lobo. a pest deck that buried the pests before I got scarabs out, a fire deck that did a lot of very quick and pumpable damage, and mono-aether once the shields go up.