Yes its worth slotting but only with 1 extra slot as a 3rd slot only gives a 2% return.
Defiant's GoEH/MILITIS METUS
It's not worth slotting it. You already have a high Nrg res and spending 2 slots will give you only 3~4%. It's even lower for Neg res.
If u intend taking power surge ur energy protection is 257% so 5% is not worth it (negative energy is 175% with 3 slots and 140% with 1 dam res). This over 100% resist only helps if u decide to jump into a squad of nulifiers who shoot u with -res, stay long enough with some mobs out of your AoE range u will die suddently. Considering most brutes Ive teamed with think they should be able to do just that and not die, it may/may_not be worth it to u. In pvp u wont get that volume of -res, at least I dont remember being effected by a -res in PvP.
Same with slotting health, I tested it by letting 2 of my enhancements turn red. I then dropped from the sky, and timed the recharge. I got bored waiting, so only timed it up to a point near halfway (in line with a letter above); and guess what? When I tested with the 2 slots with green enhancements the timing was so close that it could be down to testing inaccuracies.
I still take health, u do notice it at lower lvls; and hurdle has no benifit for me.
Those 2 slots will be better served slotting your attacks.
The only place Ive seen a noticeable difference (on paper), is looking at slotting power surge. With 1 resist, most resists are over 100%, but toxic is 63% and 3 slot its 81%. Considering this is the only toxic resistance /elec gets (apart from demonic aura/inspr), u may find it worth it.
Okay, so, I've gotta take Grounded on my Electric Armor Brute for the knockback protection... but I'm wondering if the Energy/Negative resistance is worth slotting beyond the one default slot. Should I expend another 1-2 slots of Resistance on it, or is the bonus too small to be worth it?