Hey :P I play both morde and pantheon a lot, so I hope that will help XD
Pantheon is a cool guy, he can harrass well and cna do tons of damage. On the other hand, he's squishy. That's why i strongly recommend the common cleanse/ghost combo. It really helps. Once you have that, you can play super agressively
Pantheon is good for his global ultimate, but you'll need some practice with that. His limitatins come from the fact that he can do only phisical damage, and you can be exhausted. Even tho you should have cleanse, i don't recommend wasting it to remove exhaust - in a battle you'll need to save it for the hard CC.
On the other hand, he has vast potential - a way pulled ult can deal 1000 damage (before resistances) to all the guys in a fight + a nice slow. Your AoE spell can be devastating with the right positioning. He can be an effective carry.