Venusaur SW.
Seriously, it's not a bad card when you play it right. Using Time Skip every single turn and focusing a deck around that strategy is obviously bad. With a Dialga Lv. X deck you should take into account the possibility of Time Skip backfiring, but you shouldn't rely on it.
Only use Time Skip at crucial times, when you can afford to not attack, your opponent can't afford to miss a turn, or when you'll lose otherwise. With Venusaur, you can limit the potential disadvantage if you need to use Time Skip, while allowing you to knock out Pokemon with poison or burn, and get a chance to use Time Skip without any risk. Also, it has high HP, as well as a healing attack.