Except for the fact that I'm terrible at most of the bosses in Dark Souls 2, and needed to summon for almost all of them. Let's just DS II has a lot of Smough and Ornstein-like bosses.
The only boss that gave me a lot of headaches, sans O+S was the Bed of Chaos. Just running back everytime I died was a pain in the glutes.
The way I see that boss, you WILL die at least 3 times, unless you're skilled at running back after each orb. :I
Stick as close to the boss as possible while going for the orbs and block. Only the firey stuff is unblockable and staying close both avoids the floors and makes chaos use her wooden hands.