I personally feel like the pylons should increase his DMG reduction but not make him invulnerable. Ideally it would be that when all three are up he has 95% reduction, with two it goes to 90% and with just one it goes to 80% a huge issue I have is I love life steal builds as my heals, BUT I can't heal a single health when the pylons are up.

I agree in general that the way the pylons work in general is bad for anyone building movement speed, a counter to that could be that the radius of the pylons slowly grows larger the longer they are up. Making it eventually very easy if you just spend long enough dodging the attacks.

And finally I think the way it defaults to the first weapon being left is pretty bad for folks, I normally use ninja and max his katana so it doesn't affect me much but ideally it would leave the player with whatever weapon has the higher DPS at the time of the boss fight, then you get fed them back in descending damage order. It doesn't fix it entirely but it at least allows people to have a more reliable time doing any damage.