Didn't everybody hate respawning outposts in Far Cry 2? I get that it feels empty once most outposts are taken, it's just a bit ironic.
Tis ironic, though i think the problem is they went for the two extremes. I liked the re-spawning of far cry 2, the problem was that there was a lot of travelling back and forth and they re-spawned incredibly quickly. Not to mention it was the same group of people every time, and then you have to hang around for the crazy suicidal-driver who comes charging into you with a car.
Far cry 3 was enormous, open and quite frankly a joy to travel around, it just became pointless and boring because after a while due to zero chance of enemies. For a game with a shed load of collectibles which had you travelling far and wide, it's pretty boring when you know you won't find a single enemy.
I'd prefer something a bit more dynamic, where enemies can spawn around the map and reclaim outposts, it just needs to be occasional and random, not just a straight respawn two minutes after you've left.