Geppetto vs nightmare last boss

[Mortimer]

So I've made it to the last boss with Geppetto. The way was pretty easy, got nice build, died like 0 times, my scoundrels have annihilated 3-rd boss in one minute... and I've died on 2-nd phase of last boss, because of full circle wave attack. My defense shield just wasn't enough to block it completely and I had not enough time to heal up before next wave attack. I've done it with Piper and Wukong before and had no problem, cause their defense just block/ignore this attack. Am I doing something wrong? Is there any way to evade this attack? I know about broom and I've tried to roll it, but random was against me. I just don't want to believe, that you can't kill boss with Geppetto because of one item, there should be some alternative.

[Mortimer]

I mean when you die from any other mechanic like bullet hell or beams - it's skill issue, you can learn how to evade it. But this attack can't be evaded without broom (at least with Geppetto). Feels little unfair.

[Rilwing]

You get a few i-frames at the start of your defensive skill. Timing is needed to avoid this attack.

[Mortimer]

Originally posted by Rilwing:

You get a few i-frames at the start of your defensive skill. Timing is needed to avoid this attack.

So, he actually HAS i-frames on his defense. Cause it looked like he doesnt. Thank for the tip.