Lol , GP's E is perfect to engage on the enemy for ganks , it has huge range you can effect your allies from far away , and since it is passive you ain't feeling it's effects but they are very strong.
It's like Sivir's ulti in a normal skill edition. I don't think GP suddenly got UP now but he won't be so deadly as he used to be.
About Pantheon yes i believe they will boost him , they told it 999 times that they are re-looking the old champions , fixing their broken/old stats and as you can see they are doing it , and it all started from Alistar.
Dunno that changes they will do on Pantheon , maybe increase the stun duration of Lv1 [W] so you won't be forced to lv up it so you will level up [E] and be able to do your combo before you go 9lv ? Dunno , we shall see