[guineapig]

I play a tanking bard... mostly out of necessity (cause there is never a tank around when we need one).

Staff of Writhing + obsidian Dagger in the offhand.
Snare/slow song at the beginning and end of the fight.

That's pretty much all you need to keep aggro on just about anything. If some caster gets super silly aggro somehow then just chain mez the mob you are attacking.

Otherwise, damage shield song is a good idea to make your DPS look better (since our DPS is generally shite compared to every other dual-wielding class.

Tanking is very doable in classic as long as you aren't taking on mobs above the mid 30's. In other words we can handle Solb Kobolds and Lguk bedroom-ass/sup area.
After that you start to become a bit of a drain on the clerics unless you are able to consistently pull singles and have everything perma-slowed during the fight.

I don't think you will be hitting 900 AC without raid gear so I wouldn't make this a goal till you are already level 50 and looking for something to do.