If tanking their breath is the problem you could get some resistance amulets or use the lord stone.
* You didn't mention Shouts, so I assume they're permitted. Use Whirlwind Sprint to get in close, or Become Ethereal to save yourself when they're breathing at you.
* If you're not using enchanted weapons, use Elemental Fury to increase damage done.
* Get a well-smithed weapon, the best you can afford and create.
* Try to approach the dragon from behind. Its tail it less deadly than its mouth or breath.
* Don't be afraid to use a companion. If nothing else, they give the dragon something else to attack.
* If you're in trouble, go inside a building and wait for your health/stamina to regenerate.
A good tip for fighting dragons on the ground is to bash when they are about to do a shout, they will get dazed for a few seconds which gives you a good opportunity to start hacking away at it's scaly hide.
Use terrain to your advantage. Wide open areas are dangerous, but you also have more of a chance of a Dragon landing to attack, just make sure there is some form of cover.
Time your block bashes, you can stun lock any grounded dragon that way.
Use shouts to your advantage.
Doing two-handed can be challenging, because dragons don't usually land unless there's space, and this can be a big problem for you if you don't have cover.
Learn to kite dragons, meaning you dictate where they land. Try to get them into open areas where you can take cover when they start their attack.
I stick to the rear of them, because trying the sides can be tricky as they can turn fast. Fire breathers are the worst, because they can obscure your vision, especially at night.
When you learn to control their behavior and patterns, taking them out won't be too difficult.
Also, pay attention to their attacks if you should accidentally get in front of one. They all have them, and they can be very deadly if you're not careful. But this can be an advantage, too, because they'll lunge forward enough for you to get a few head strikes in before they rear back and turn.
Good luck, warrior!