There's not much point having 10 elemental shamans. 6+ Shamans will global any character with shocks or lightning. However, adding more classes doesn't really provide anything either. The other (horde) healers/casters are too squishy and adding melee would be annoying to manage.
I'd probably just swap a couple of the shamans to resto to spam chain heal and provide mana tide.
Set a hotkey for and get used to using the "line formation" keymap. Pressing once will split your team into two stacks so your entire team won't be stunned by one grenade.
