It is a reasonable (or should i say good) card, but not often used. Earth has 2 midrange attackers, the graboid and the golem. If 12 is not enough for you, you might use some elite shriekers or dragons. That does not mean the antlion is bad. There is just a lot to choose.
Objectively, you get 4 attack for 2 earth upped, and the unit can burrow. (Which admittedly I do not need often. Please..attack the antlion I say because who needs 2 damage from a burrowed antlion?) Only the upgraded frog (life) is better. There is no way you can say the antlion is underpowered. The crawler (water) or the mercenary (gravity) can't stand in it's shadow when it comes to quants/damage ratio.
Life and earth do not have much to complain. I would rather leave this alone and give the gnome rider some ability. The elite antlion is actually not a bad attacker. 6 golems and 6 antlions do the same damage as 6 shriekers. To compare: 6 x 4 = 24 and 6 x 2 = 12, total 36 cost. Shriekers: 6 x 8 = 48 cost, and less hp. And it is very funny to use a rush deck with 18 attackers I can tell you. (+ 6 graboids!)
If you must change it, please ditch the burrowing. It's an antlion isnt it? I would love it if it ate parasites or devourers, or 1 HP critters even. I probably won't mind a cost increase then.