My suggestion is this, should a failed spell initiate combat? It's not like a charge where if you miss you're still running at them with a weapon...as far as the target knows (unless of course they can comprehend the language of magic) you're just trying to make yourself a meal. Now yes this will have an up-side and a down-side. For one you won't start off a fight with a fluke spell and ruin your chance of getting a first hit, but also it means if someone comes into the room and the mage is spamming a spell if he fails it doesn't ruin thier chance of getting the jump on the mage.
Failed Spells
This isnt a realistic issue, its a balance issue 
To allow mages to always get the first hit basically, which is what this would mean, would be unbalanced.
Doesn't actually give the first hit to the mage, if the mage fails you know he's trying to attack you and it gives you a chance to charge or throw in the first hit. If he hits with the spell then battle would have gone like normal. Races with comprehend languages would know instantly, while your melee ones might have to remember what some spells sound like when being casted. As far a communers go....
Experiment a little, some spells as well as skills when failed will not initiate combat.
On the subject of failed things, how about we make it so that if you trip a trap and it misses you it doesn't lag you? Thats pretty redik imo
you know whats hilarious, if you open vs a cleric with spell turning up with something like dispel good and your evil, nothing happens and they can just walk away even after the Die Bryntryst's Momma your sorcerous dog! yell.
Also, think of a trap not hitting you and you still lagging, as you dodging or avoiding the trap as it springs.
ahhhh, still annoying