Well, I think the opportunity to use the resist 10 function is going to be fairly limited given that a character in the thick of combat is hardly going to want to burn their one standard action on the CHANCE that they will need to resist damage. In almost all cases it would be far better to simply use the standard action to beat down your opponents, thus denying them the chance to DO the beat down in the first place.
There are times however when it will make sense. A defender facing a strong opponent whom his particular attacks aren't very effective against for instance. He can simply power up the resistance, tie down the monster, and let the strikers worry about killing it off, his job at that point is just to be a blocker. The only real weakness there is that fighter marks expire at the end of the character's next turn, so it will either require burning an AP or having some sort of move/minor/free/interrupt way of marking. There are ways to do that, though they are not all that easy to come by. I would observe that heavy offense fighters might consider building their character in such a way as to allow for that, and Bloodcut Armor thus becomes an interesting item to build around.
It's a minor action to activate the armour (only when you are bloodied.
Our ranger used to great effect - he got surrounded by 5 skeletons and chose to activate the armour on his turn after he had attacked. The skeletons all attacked him on their next go - 4 hit but he only took 2 damage.
I then used an action point to centre two AOE spells on him - he took 1 damage from 1 of the spells, but the AOE killed 3 and bloodied the other 2. On his next turn he just moved away (provoking opportunity attacks from the skeletons) took no damage then unloaded his bow into them. The armour power then ran out at the end of that turn.