To elaborate, savage melee has a mechanic called "blood frenzy", which provides a recharge reduction and end cost reduction buff with each attack, then some powers use up these stacks for added effects. I tend to try and maintain the stacks, as I much prefer the buffs than the bit of extra damage or other effect you get from using up those stacks.
With regard to the armor sets, look at it like this:
Radiation armor is the more straightforward of the 2 armors I mentioned; It's mainly resistance-based, but offers a self heal and end recovery buffs, not to mention a fairly power absorption shield and a self heal, to keep you on your feet and fighting. You also get yet another recharge reduction buff from the set, so in conjunction with savage melee, you're powers will be up & ready very often.
Bio Armor is a bit different - It does much of what radiation armor does, with the key difference being the "adaptation" power. This power allows you to switch between 3 different modes - efficient, offensive, or defensive. These modes impact how your other armor powers function - they can even add additional effects or boost your own damage. You get a little defense, some resistance, and other effects.