Well while you're in they middle of a fight being able to chug aan unlimited number of potions is kind of ridiculous and essentially makes you immortal. Just cheapens the game in my eyes.
I have a similar rule about using health potions or any potion at all except during crafting.
There are a number of ways to deal with dragon breath.
Having high magic and elemental resistance helps lower breath damage. You can get them easily via a large number of ways. However that not what I'm here for. That way you must have already know, what i'm here for is to teach you the secret techniques:
1. Spell breaker. It throws out a ward far more powerful than it's description suggests. It is by far, more powerful than what a restoration master can throw out.
2. Ethereal shout. Get talos blessing and amulet. If you have the morokei mask fix which uses the real morokei enchantment (100% magicka regenerate and 20% faster shout cooldown), use that as well. Using only the first level of the shout should allow you to go ethereal whenever dragon breath is incoming.
3. Atronarch standing stone + breton's dragon skin makes you invulnerable to all magic (including dragon breath) for 60 seconds. Kill him within the time.
4. Conjuration/companions and invisibility. Invisibility WILL force the dragon to switch target even if you are almost immediately detected afterwards. This is how shadow walker works.