Hm, not sure I understand you but here is the thing:
1. From 1-2 VUs now, you don't waste decay air shoots, so it doesn;t matter if you miss a target or not, or even leave auto-fire on dead mobs, until you target another one
2. You can use "Select Next Target" action to tag the first mobs in range
3. You can click on the mob in cursor mob to tag it
In using the above action, points 2 and 3 it's up to player ease of use, there is no other difference in them
I personally choose "Select Next Target" and if I have more than 1 mob on me I use click on the target in order to make sure I tag the desired mob
All in one, not sure if I answered your question, but hope I helped you a bit