I'd like to adress some things you mentioned and give some tips:
First of all Edain hotkeys are streamlined: In the ui from top to bottom the ability's are bound to y x c v b ...
Furthermore if you have units selected you can use the "e" once to select all units that are the same than the ones you have selected that are on your screen and press it twice to do the same for those units mapwide
Spreading my units so they are not vulnerable to AOE spells
If you press "R" all selected units split. Prob usually worse than good manual splitting but useful nonetheless
Using single units abilites
Changing unit stances
Regular "cannon fodder" untis should not have abilities that require clicking and if they really need to have them there should be an option to click them globaly.
Usually if you have units selected that are the same if you use the ability for all of them, this is were using "e" to select those units can be useful
Reading tool tips for hero abilities.
Each faction has many heores and some heroes have even many forms or pages with abilities.
Well ofc if you're new to an rts then you have to learn a lot of new things, Hero-abilitys are just something you have to learn
Buying banners for newbly made units
Not sure what you're problem is with that, you can buy upgrades for multiple units at once and it still possible to do that if some of those already have those upgrades (only exception are eregion blades and eregion arrows of Imladris)
All his abilities have similar images (mouths) and for me it is hard to memories with does what. I rember that there was one that weakne heroes but I have to pause and start reading tooltips in the middle of the game. This is terrbile.
True those ability should get better icons, but most icons are pretty good I think
Make abilities color coded.
I agree with what necro said here, furthermore it wouldn't remove the fact that you usualy have to know what an ability does in order to use it, and like I said I think most abilitys are easy to learn/remember and recognize by their icon.
Overall as an fairly experienced player I don't think there are to many things to micro; I hope the things I mentioned help you to better manage lategame micro