I find any ally with ranged abilities will pull agro more. Melee is still bugged where they do not get close enough in range to hit anything half the time.
If you manage to give them lots of AoE (Fire Control + Fire Blast for example) they should be able to hold agro quite nicely unless you over power them.
If you out DPS them, or have any taunt in your attacks, then you'll take agro from them. I'm not sure what the benefit would be to having them hold agro this way. Their DPS subtracts from your exp/inf gain. If you want something that will grab agro and survive, I recommend using a control/defense combo. Personally, I make control/buff allies so they mesh well with almost all ATs.
Freeedom
H: Victra Defile (Rad/Dark) & Hot Hits (Fire/SD)
V: Spike Cream (NW) & Crescent Wind (Nin/Storm)
Sub Hero Inc ARC: 1541
--If you don't like what I have to say, it was probably a typo you are refering to.
How well or poorly do Ally characters with Tanker-type powers hold aggro? My testing suggests "not very well," which makes me think they lack the PC-Tanker inherent aggro management abilities.
Which I suppose would be a good thing, as otherwise it'd make things too easy for players. But in general, how much should one expect an ally to "take the heat off" of a player?