Man. I just recently fought this boss, and I died 3 times until I could finally defeat them without using any buffs. Even though I can now defeat them without much of a problem, I'll admit that they were the 1st boss that I fought in Terraria to keep me on my toes since Cave Story I guess. There seems to be a bit of trial-and-error involved with figuring out how to defeat these hardmode bosses, and even if you've figured out a way to dodge their attacks, you'd still need to put your platforming skills to the test.
Edit: They may have even kept me on my toes in a similar way to the various optional superbosses from Kingdom Hearts, including Sephiroth, Kurt Zisa, and Phantom, and those were some pretty difficult bosses to defeat. Perhaps we should consider these hardmode bosses as more like Terraria's superbosses, since they actually require quite a bit of effort to defeat, even with endgame hardmode items. It definitely seems as if Re-logic is taking the easy-to-understand, challenging-to-play, difficult-to-master route here, and I like it. :D