I've had company over the past couple of days, I'm planning on making a movie specifically for dual-boxers to show in game footage strategy of the "sweet spots" of where to be on each map - with lots of commentary instead of music
Also your spell damage is high enough no one should be able to heal through your damage, sounds like the opposing shaman was minimizing your damage with grounding totem.


Nagrand


#1 spot is against caster heavy teams, utilizing the pillar to minimize their burst potential.
#2 spot is against melee heavy teams, forcing them to come to you, making them unable to LoS you.

Blade's Edge


The blue outline shows the optimal areas to stand, the direct middle is bad because they can just mess wit you on the bottom throwing spells, but on both sides forces them to come up top and duke it out also they cannot LoS you, only jump off which means they left their team behind.

I couldn't find a good picture of Ruins of Lordaeron, so it'll have to wait until the movie