Ahum, don't know which game you've been playing, but orcs are very very strong, I'd say the best coherent hazard strategy around actually (because of keyability). The number of times I've squashed or been wiped out by orc/uruk lieutenants, with two or three tribes, been sniffled by an orc scout...This is what virtualizing cards is about, improving a weak card to enhance a weak strategy.
But true, the Great Goblin was only in the deck for fun, if it was at all, so improvement is needed.
Adding strike is big, even to orcs that generally have many strikes, but it makes the lieutenant viable without minion stirr, and that's big. Playtesting will proove if it's too big. It's now modelled on Spider rather than FoF, which is suitable indeed for a unique creature and I prefer strikes to prowess, however keep in mind that the playability of spiders is much smaller....
I did like Jambo's suggestion of the orcs tracking a company down, but I suppose he meant a company moving from Goblin Gate (or the under grottos?), not just having visited the place some time during the game and anywhere over the map.
As I understand it, the bonus still works for himself when attacking in Anduin Vales/Rhudaur, with DoN...
I think, that if it's a creature that creates an attack, you should be able to kill it. So, along Balrog lines, you should be able to go to Goblin Gate and kill it. Otherwise there is no way to remove it, only marvels which is a bore. It doesn't get discarded when you cycle, nor when you defeat an attack...so this would counterbalance the use a bit. It's unique, but with Uvatha/Mouth you can get it back easily after all. Having to battle 3x minion stirr and this card is Too Much to Marvel.
"if played as a permanent event, any non-unique orc creature can be keyed to High Pass, Goblin Gate or the Under -grottos. With Doors of Night in play, any non unique orc hazard can be played keyed to Anduin Vales or sites therein."
I think an ability in stead of the general +1 strike along this line could be cool as well, maybe less powerful but thematically cool and usefull too. This way you keep it a bit more thematic, Great Goblin is a local warlord, not a general source of malice.
Play orc-guard on a company moving to Eagles Eyrie from Lorien, for example. Could also be extended with wolf-warg creature, though not many use this combination and they can usually be keyed anyway.
Other option: "any orc-hazard played keyed to ...doesn't count against the hazard limit."
Granted, Umi/Bumi and 2or3 tribes does the same, but it could still be useful, Anduin Vales is probably the most frequented region on the map, so that's no minor feat, and you don't need to hold on to those cards.
Not sure if sending the orcs to Rhudaur is a bridge too far, the Elves wouldn't suffer it and our Goblin is no Witch-King.