It is imperative to make sure the proper bar-spell is up at all times, preferably being cast by the member with the highest level of enhancing magic skill. This will greatly reduce the damge from avatar en-spell as well as their 2-hr.
Also, keep in mind that all enfeebling magic, other than spells of the element the avatar is weak against, will be resisted. This includes dispel. Garuda, for example, will resist the following spells: Slow, Silence, Blind, Flash, Dispel, Gravity, Choke, Rasp, Drown, Burn, Shock. Bind, Frost, and Paralyze should land with little to no problem as they are ice based (ice strong against wind).
Other than that, there's not much to these battles. Try to work out a skill chain and MB that the avatar is weak against to maximize damage, as they are quite resistant to melee damage. Keep the tanks healed, the proper bar-spell up, working enfeebles applied, and just wear them down.
Edited, Thu Aug 25 20:04:33 2005 by Spielmannsfluch