RedRein

Indomitable will has-
1. 10000.00% resistance to knockback on self Ignores buffs and enhancements unresistable.
2. 10000.00% resistance to knockup on self Ignores buffs and enhancements unresistable.
3. 10.00 knockback protection on self unresistable.
4. 10.00 knockup protection on self unresistable.
5. 10000.00% resistance to repel on self Ignores buffs and enhancements unresistable.
6. 10.00 repel protection on self unresistable.

The 10k KB resistance means that all incoming KB is reduced to 0, as is KU/repel. It's the same as getting hit by a mag 0 hold, it does nothing. So far the only unresisted KB I've seen includes Ghost Widows Soulstorm and Self-destruct. KB IOs wouldn't help either of those.

Willpowers do not need Knockback IOs, they have 1000% res to KB. Quicksand is good for disruption and -def, it's worth picking up.
Getting burnout is a great idea because you can quickly get double rage stacked and when your Strength of Will is about to crash, you can use it again.
Also, get t4 reactive interface (75% fire DoT/25% -res) to increase your damage.
Finally, Stalagmites only has a 10% chance to stun and rarely does, I would not recommend it.

Worth noting my main is a PvP Wp/SS Tank.

Firstly you need to understand that pve and pvp are very, very different from each other. Second, look into the Diminishing Returns curve then try to rebuild the tank.

-Here are some tips-

Do NOT get rid of Rise to the Challenge, it increases your regen rate so much.
Do not get Leaping. I understand you got that for Combat Jumping's +def but find another way to get that def(set bonuses).
Defense isn't everything in pvp unlike pve. You need a a lot of resistance and hp as well.
I prefer Earth Mastery over Energy, but that's up to you.
Do not get Leadership for Maneuvers, too much end drain. Get Stealth+Phase shift instead.
Get Aid Self. Keep in mind that this power can be interrupted, so if you are having trouble healing then Phase Shift and heal.
Finally, do not get Foot Stomp and I would not recommend Hurl if you take Earth Mastery.
It's all about speed in the arena. You would be surprised on how much more damage the fast recharge, minor damage attacks do than the long recharge, long animation big hitters.

Good luck!
See you in RV >=D

Tanker for more survivability for a longer period of time than a brute and you will have moderate damage. Brute for less survivability, unless you are in t9 but then again the survivability is limited to a certain amount of time. If you have a brute build that makes you sure you can kill the opponent in less than 6 mins(with burnout) 3 min (without burnout) then go brute. After all they do have a bit more damage than a tank.
It all depends on your style=]