I do not have to much trouble with my guard and agro even in unlinked encounters. Not sur on what line you went for AA's but I found with Warrior AAs, I took my AGI line to the AE ability, then strength for the hate gain and haste from INT or WIS (cant login to check atm). Then I focused on Guardian AAs for doubles attack and then went on the debuff lines as I find debuffs tend to stick a mob to me near as much as dps.

Putting my agro reduction on the biggest agro threat helps to of course and I have hate transfer from Bard. I might be wrong but dont Wizards have a hate transfer also.

A lot of DPS also have some sort of hate reducer also which I tend to mix in with their dps macros.

Standard ae fight for me with on guard is.

Make sure hold the line is buffed.

AE taunt > Reinforcement > Assault > AA AE attack > Taunting assualt > Guardian Sphere. Rinse repeat.

You can fairly much nuke AE with your other toons from the Assualt as if they rip agro your Reinforcment should re prioritise you on the threat table with the AE attacks.