Glad & proud doit.im pro user here.
I would like to reference this case - http://help.doit.im/topics/1201
Basically this earlier case is also about the ability to batch-tag multiple items. A solution was proposed to the user - the mac app has this ability, but only the mac app. And since the user had a mac available...

I do appreciate the fact that the most of doit.im devs use macbook retinas and whatnot ;) but most of your users is probably android/windows crowd - and so am I. I've got an android smartphone and a windows 8 hybrid device. The windows doit.im app is sloooow. No offence, just saying - it's probably snappy on an intel i7, but mine hybrid is an atom slate, so you know.. ;) I use the web version on it. And I'd really like to see batch-tag on android and web version.

Kind regards