Just my philosophy, and there are people who agree with me.
There's a bunch of people who think the world is flat too

(note this is not a serious comparison!) From an efficiency perspective, you only need enough defensive capability to keep everyone alive. My healers don't have defensive AA's after nearing 1000aa's.. they just don't get hit unless the tank dies and I'd rather not prolong the agony. You can make an argument for defensive aa's keeping someone alive in the 5% of cases sheets hit the fan, but there's a counter argument as to how often sheets hit the fan. On THF, the only classes that can tank for more than a lucky heal in tier appropriate gear are War, SK, Pal, no matter their aa's.
A single group with
one of the more useful donors can make it a long way. Personally I'd highly recommend for either the shaman donor v.1 weapon, or the SK v.1 weapon if you use an SK to tank. Both provide a 1500 per tick group regen which will give you enough of a boost to still find the majority of tiered content quite challenging, whilst making it possible to proceed all the way to T6 if you get tactics right. You could instead get Pet class BP donor items (Nec or Mage), but the pet donors are vastly more powerful, and you can use them to effectively 2 or 3box your way to T6, which is a bit cheesy IMO and you miss the fun of exploring well designed and interesting content which took a couple of years to develop (it's a case of traditional tank/heal/dps group dynamics vs heal-the-pet).
One of the downsides of an EMU server is that you don't have a large dev team pumping out content. To any new players here who want to experience the server for what it is, I strongly recommend not racing to the top as you will quickly get bored having missed all the fun along the way.