I use focusframe addon to see and watch my focus. I bet using anything with focus in it with no focus will fail, so check to see what your focus is before using /assist focus. Also, it doesn't target your focus, it will auto-target the focus's mob, so if your focus doesn't have anything targeted, then when you /assist focus, your alts will clear their target....just like your focus.

I don't like to EVER target mobs, so I use focus on my main and then my alts use:
/cast [target=focus-target] DPSSpell for DPS
/cast [target=focus-target-target] HealSpell for healing
No targeting, no changing targets, no worring about names, no worry about who has aggro.
I also can still kill things even if my main dies. He can still target things, so the alts still just kill whatever my main targets. No need to change anything.
You can shorten, but probably achieve same results in the assigning focus part, try (might need a tiny adustment, I am at work):
/focus [target=party1, nodead] [target=party2, nodead] [target=party3, nodead]

For totems, I have a lay all down button and seperate lay all of one kind down buttons. I have 2 melee and 3 resto, so
/castsequence reset=combat/16 Stoneskin Totem, Healing Stream Totem, Grounding Totem, Searing Totem (for main)
/castsequence reset=combat/16 Strength of Earth Totem, Healing Stream Totem, Grace of Air Totem, Searing Totem (for melee alt)
/castsequence reset=combat/16 Stoneclaw Totem, Healing Stream Totem, Grounding Totem, Searing Totem (for resto's, but 1 uses mana spring)
I have the melee alt put in a poison cleansing totem instead of a healing in BG's, so rogues can't auto-win. I also use it for mobs (spiders, etc).
Just leave out the parts you don't have yet.
I then put 4 healing stream and 1 mana spring on a hotkey, same with 5 searing, same with 4 grounding and 1 grace of air, etc.

Good luck and hope that helps.