I heard the guards in KATTA castle are great for experience.
Does anyone know what they are called and if a lvl 56 Druid could solo them?
I hear there are Centurions and then Legionares............which would a lvl 56 Druid get experience from safely and which could be solo'd at level 56?
Where in Katta do you find them....is there lots of aggro or can it be solo'd safely.
I dont see many posts on any websites for some reason about these guards.
What exactly are they called then?

With my necro alt I hunted Katta guards near the graveyard. Easy kills, exp was good, nice pp. I started around level 50 or so.

I dont like hurting factions if I can avoid it with my druid though, so I havent hunted there.

Root rotting or nuking should work fine there. They hit hard though. Pull from the church walkway, there is 1 roamer, kill him first, then kill the stationary guards. Avoid the graveyard, it pops nasty little undead, stay on the walk.

Rather than root-dot, you can charm one of the two sonic-wolves in front of Nathyn's Manor to keel with. They're very effective (healing them isn't too big of an issue), and the Manor itself is a great place to hunt. That, and Legionaires in the streets are all good. You'll probably wanna stay away from the Centurions, who guard the larger buildings, as they summon (or at least the ones I've run into do), which can be an issue if charm breaks.

It's good money with the armor drops, probably good exp at 56, and most importantly, a good time.