The randomness of Boss mech can cause vuln you can't avoid?

[Rikka_Chu]

There is not much randomness to it, there are like only 2 or 3 patterns he drops these aoes, and you can avoid all of em without getting a single vuln stack.

there is a random order to the placement of the cacti and a random order to the aoe's that the mob uses and it seems some times these two can end up with a config where you physically cannot avoid

Yes you can. in both safe spots there is enough space for 2 ppl on each side to spread avoiding overlaping aoes, these aoes around player happen when there is no knockback mechanic so you have plenty time to adjust. I'm not 100% sure right now but as far as I remember aoes around you explode 1 sec after cactus aoes, so there should be even more time to adjust. just wait for cacti to explode and spread.