Addition to /cast
 

Was working on my DPS rotation for my Arcane Mage and was looking for a way to simplify the clicking.

Would be really nice if they added an option that let you modify what spell was cast based on buffs/debuffs were active.

They already have a few things that could count as buffs (Stealthed, Flying) so why not expand it.

for example:

/cast [no TDebuff:Improved Scorch] Scorch; [PBuff:Missile Barrage] Arcane Missiles; [PBuff:ArcaneBlast:2] Arcane Barrage; Arcane Blast

TDebuff = Target Debuff
PBuff = Player Buff

Very little real "automation" could be done with it, but it would help make rotation efficiency just a bit easier.

Actually, plenty of automation is achieved by doing that. You'd be making the game think and make decisions for you, instead of you choosing on your own. This is precisely why buffs aren't conditionals currently.

Back when 2.0 came out and they removed the ability for scripts to cast arbitrarily, they justified the [form] condition by saying that stances/forms/stealth change the player's ability to cast certain things, and it made sense for macros to be able to do different things depending on which one was active.

So that's Bliz's answer: "buffs" that don't affect which spells you're allowed to cast can't affect macro cast decisions (for the same reason that active debuffs on party members/targets can't affect spell/targeting decisions).

Edit: I just noticed that you actually did ask to be able to be able to check target debuffs. Abuse of that ability is 95% of the reason that the current macro system was put in place, replacing CastSpellByName and TargetUnit as player-usable APIs -- so I highly doubt you'll ever see that come back again.