General

and to add onto what @panda143: said, you can also pot in DS!

As you're about to get hit (or see the animation he makes when he's about to do a dash attack), use dark sight and that way if you do get pushed back and there are meteors behind you, you won't take any damage other than the initial charge attack damage.
Using dark sight is pretty much the key for any thief in magnus, since you can avoid meteor damage and the green gas paralysis (you cannot avoid the green/yellow laser skill however, so jump away from that).
You can also flash jump while in dark sight so dodging attacks is possible.

Well i solo'd him for the first time a few days ago(im pally btw) and it was a pain in the *, i only have 300k range selfbuffed(im still using empress till i finish my RA set and my tyrant cape) and even using bind and god mode(scarosanctity) i had only 3 lifes in the end of the fight, even when with the first life i took half of his hp, so its pretty damn hard, but practice with the easy one till you get a strategy and remember to run away from him when he dash or when the gas is about to get u, bcuz thats a insta death, i think if u use dark sight u can even dodge the meteors...

at least when I went a few days ago, he's bugged. his dam rush attack hits you twice in 1 sweep so you're stunned for 3 whole seconds and is ridiculous. not worth trying atm (well, Normal Magnus. easy is fine but he's Easy)

I thought classes with stable DPs have it easy compared to zero, but boy was o wrong.

Use Showdown...? o.o

Step 1: be a zero
Step 2: op dash skill to dodge
Step 3: win

ot: When he dashes, don't jump. accept that you are getting hit. hope that there aren't meteors behind you. get knocked back, pot, keep attacking. gl

I have 600k clean and it's just frustrating. I've tried twice but something always messes me up. It's usually his dash attacks.

watch videos and practice, also define enough damage, i would suggest 350k clean to be the minimum