Originally Posted by Katophract
In the Alexiad Anna Komemne talks about her father fighting the Normans. Alexios was armed and equipped as a Katophract. It mentions an incident when he was surrounded by enemies and was struck several times by spears. "His horse bolted" and he made an escape but with three or four lances sticking out of his armor. None of them penetrated. So, we can assume that the armor of the kataphractoi was pretty effective.
True, but it was such a minority in the Komnenian army that they couldn't do as nearly as much damage as the kataphraktoi of Phokas and Tzimiskes. Macedonian-dynasty offensive armies were primarily cavalry with infantry in a support role. By 1100 that role had probably switched as kataphraktoi became more expensive to maintain and train.
So yes, they were the super-calvary of their day, but by Alexios I's reign they weren't as important a factor.