This card actually has excellent attacking potential! On average you'll get one heads every time, so that's already 60, just like Donphan. Victini with Victory Start can help give you a second chance at double heads, which deals 120 damage!! That's on par with Kyurem EX's Hail Blizzard, just to put things in perspective.
The second attack will come in handy against any of the big-bad basic decks using Skyarrow Bridge as well.
90 HP is, again low, in this format, but Marowak can quite potentially OHKO monsters so fast, your opponent will lack the Energy to attack! Its a shame that this card was completely overlooked during the HGSS-On format, and we've only got 2 months left until the shift to BW-onward!! Mmm. Makes me pretty sad...