I haven't played my AT's in months until recently and it's been fun. Soldier, Marksman, and Unleashed.
I steal agro from 2gm spammers with my Gat on my Soldier, which, I spam from 100' and never run out of energy. After being in melee range so much with Deeps it's nice to be at that range, The Soldier's Concentration stacks build 50x faster too. Marksman is like the Fred Astaire of Soldiers.. Unleashed... well.. his damage puts my FF melee's damage to shame and I have over 100 points in Con on him (non SS).
As for the Behemoth... I Can build a better Inferno and so I never play mine and might delete him. The only reason he's survived so long is he's the second toon I ever made. I've heard good things about Behemoth's, like the Con primary, not thrilled about Rec secondary but oh well, and I want to tank with Enrage for awhile vs. IDF which is what I'm used to. Plus if he can out-agro my FF tank, that would be ok too.. Plus, I'm kinda in newb mode and this would be the easiest way for me to do it until I can get a slot for the Electric FF I want to make.
*shrug*