If all else fails buy life pills instead of normal potions, these have a reduced cool-down so you can use more pots to survive the encounter (these are expensive!).
The other option is to level past the content and then go back for the boss once you have better equipment, more skills and can take the hits.
Early game can be difficult on Mir but you will seem to gain in strength fairly fast!
If you do get stuck and need a hand, or want some advice on equipment etc please feel free to message me in game and I'll help as best I can.
XIII