Hmmm, on re-reading I see that I may have misunderstood. Are you just suggesting a change to the way the drop down list, lists things? If so, the A-Z categories are better because they are discrete, whereas the importance of a spell is more of a continuum.
Having said that, I hit a bump with my S-T category being so long it went off the screen and there is no scroll bar (can we have a scroll bar Strife?)
I like this idea and it is the way I arrange my own Healbot. Below is my current category set up, with examples (FYI my bars are normally white with black background and I play a MW monk):
1. Black = can't be healed eg. Shrine Surrender to the Void 269242
also 1. (colour dependant on spell) = super extra important eg. Temple Plague (on self) 269686
2. Grey = reduced healing eg. TD Massive Chomp 259079
3. Purple = delayed Dispel eg. Shrine Choking Brine 264560
4. Dark Blue = urgent Dispel eg. FH Oiled Blade 257908
5. Red = urgent/heavy Heal eg. WM Jagged Nettles 260741
6. Light Blue = non-urgent Dispel eg. KR Frost Shock 270499
7. Hot Pink = spot Heal eg. WM Lingering Dread 265882
8. Yellow = special eg. AD Pursuit 257407
9. Light Pink = any incapacitate/slow/etc that can't be dispelled eg. TD Handcuff 258313
10. Orange = player fail eg. Temple Blinding Sand 269970
11 - saving it for i don't know what
12 = Default Magic
13 = Default Disease
14 = Default Poison
15 = Default Curse (I custom enter all curses, although as a MW I can't dispel them, I still want to know when someone has one; as above for priorities 8, 9, 10, etc)
16-19 = empty don't know why
20 Affixes - Bursting, Grievous, Necrotic, Reaping
However, I am aware I might not be using the functionality of healbot debuffs to their fullest extent ie. I basically have one colour per priority level. So I'm tossing up changing it a bit, for example, not moving during Aura of Dread is definitely an orange player fail mechanic and I want to know that so I can remind teammates if they don't move (or to remind myself), but maybe it should be a higher priority level even though I want to keep it orange.
The ideal situation, but soooo much work, would be to have a menu per dungeon/raid/boss where users can pick any spell from an existing database that is included within healbot, then assign their own colour and priority, or icon even. Obviously, healbot is so good that it would have default assignments, but adding this flexibility would exponentially improve it's attractiveness to many.