[TRex]

Whenever Ive been in a base defence , as soon as you see the ''generator under attack'' message , most non-retarded players I see quickly run to defend / repair said facility.As a bonus, theres a chance you get xp by killing said infiltrators , but even more of benefit is that you can carry on defending and gaining more xp as a result by keeping the base alive.
I agree with Firefly , wanting extra xp or reward by simply hanging around a generator on a whim is farcical . You might as well stand in a warpgate on a friendly locked continent and say you're defending this continent , wheres my reward.
A much better use of you time would be preventing said attackers from entering the base in the first place before they even entered the door.
I've lost count of the number of times I've been to fill an ant up only to just arrive at a base to find someone filling it up. Thats how it goes, same as the one getting the killing blow gets the xp from a kill , not the 2 before that died attempting said kill.
The counter to all this is teamwork , support benefits those in a squad /platoon and gives more people the benefit of most aspects of the game.
But just turning up and expecting a reward isn't on, maybe you could be doing something more pro-active , while keeping an eye on the chat log for incusions and being on voice-coms to react quicker in the first place.