Let me suggest something that works for me. Scrap that target of target's targets target stuff, and just build a macro so when you hit the key, everyone, accept your tank, focus's your tank. Then build all your spell cycle macros like this
/assist focus
then add your spellcast macro here

I dont use castsequences, I just use different buttins, however im sure this might change as i level up

(3xshams 31)