Keen, Syp, and Tobold have got a little debate running on whether NPC companion characters in the upcoming KOTOR MMO push the envelope too far away from grouping and towards solo play in supposedly massively "multiplayer" games.
No one knows how this will play out in KOTORO yet, I will offer a random observation from my early experiences with LOTRO's new skirmish system. Skirmishes are instantly-generated PVE instances that scale for various group sizes. Players are given an NPC soldier - who is significantly less intelligent than a player or normal player controlled pet - to fight alongside them (only in Skirmishes). The pet can (in principle) tank, heal, buff, or do ranged DPS. The skirmish system scales to a certain extent with the number of players in the group, and is supposedly used to allow players to solo otherwise group-based content in the game's epic book storyline.
My character is a Champion - a melee DPS with off-tanking capabilities and minor self healing - so I promptly picked the "healer" traits for my soldier. I ran through two actual skirmish battles using the healer, and I noticed something interesting. My Champion has a defensive stance and a taunt that I have never used, because I play 99% of my time solo and don't need to worry about keeping aggro when there's no one else for the mobs to fight.
I also promptly noticed that, when we get attacked by several enemies including at least one with ranged attacks, I needed to take an effort to drag the melee foes to the ranged attacker so that I can hit all of them with AOE attacks. If I failed to do so, the ranged foe would promptly start attacking my somewhat-defenseless healer, as I would not be doing any damage to it or generating any threat. When I'm soloing, I'm generally more inclined to use line of sight to force the ranged attacker to come to me, and it's not necessarily a bad thing if it gets stuck in anti-exploit mode instead of finding me. In the skirmish, that foe would promptly switch targets and kill my healer.
In short, I probably learned more about how to off-tank in LOTRO in a single hour of playing skirmishes than I did from soloing 61 levels to date. I find it puzzling that Keen and Tobold think this feature is detrimental to grouping; it seems like the first serious attempt I've seen to address the problem of players getting to the level cap and not knowing how to play their class in groups.