No sooner than I say this, I started up killing again and when I checked it is now indifferent... it is still suspect though. Why did it take me so much longer than the other person...

There's a potential of 400 kill difference in the apprehensive range. It's possible when you started this faction group with the other person that the other person started closer to indifferent faction than you did.

faction/xp moving so slow that you think the game is broken, is indeed classic

:P

Once you get amiable you can get the key to the city and start messing with the guards :)

My Tunare Druid is amiable with the Heretics, it takes a long fucking time though. This was with countless hours of helping PL in the warrens too, so I was getting faction hits at a much higher pace than someone just leveling there with no help. Keep grinding and youll get there soon enough.

As others noted, the likely reason is the Dark Elf was close to amiable and you were not. Each of these mobs is likely only a +1 faction increase. If you were at the start of apprehensive, you would need 400 to get to indifferent.

^This. The majority of the mobs in the zone are +1 faction hits to heritics, that means from max KOS to max ally you would have to kill 4000 mobs.

Most people look for mobs that give the largest faction hits, followed by volume/concentration of mobs to employ efficient fractioning strategies. If you exclusive killed mobs that gave a +10 faction hit you would only need to kill 400 or +100 faction hits you would only need to kill 40 for example.

Kael faction pulls are a great example. Someone figured out the most efficient way to obtain CoV faction is to pull a group of 10 mobs that each give +25 faction. So every 30 minutes when they respawn you can get a +250 faction boost so in 16 pulls or less you can go from kos to max ally which can be accomplished in 8 hours mostly of AFK time between respawns.

Doing some quick digging it looks like Erudin would be the ideal place to kill for Heritics faction, tons of mobs in there give it and there's some that are show +45 hit per kill according to the wiki

Kinda hard on your Erudin faction tho :D

Despite being slow, the Warrens gives only positive faction hits, which is why its nice.