Its a relatively simple idea to solve the targeting problem in large zergs: why don’t we just have an option in the menu to make allies untargetable whilst in combat and IF you needed to target a particular ally you had to ALT+click?
This option (like all options) can be toggled on or off within the gameplay menu.
Yes I know people have other ways to make targeting enemies slightly easier like turning off player names, and CTRL+T (targeting) whilst in a party, but why not simplify it further?
And yes, it IS a massive problem- its near impossible to target a single enemy when you have 20+ surrounding it and you spend precious seconds trying to target. But this option could fix it painlessly!
I have discussed this within the /r/guildwars2 reddit page and received really good feedback about this. The post can be found here: http://www.reddit.com/r/Guildwars2/comments/1lig30/option_suggestion_make_allies_untargetable_whilst/
Thanks Anet for your continued service to this community! Love your work.