No change needed. If against devourers, you can kill them easily since they have 2hp, plus it takes awhile to get that many out in a non upgraded deck. Even to burrow them would take an extra turn and cost an earth quantum (so the deck would have to be two elements). So devourers are not overpowered at all.
If against pests, which means the situation is upped deck vs upped deck, then towers already give you quanta right when you play them, so that makes up for it. Pests are more difficult to kill, but they are not overpowered either, since they're even less effective in upped deck matches.
Also, devourers/pests are both ineffective against decks that use nova, quantum pillars, or sanctuary. All that said, I don't agree with the opinion that devourers/pests are overpowered.