The 23k is your hp, and the 25/45/50 is your Def/Shield/Abs, but what's that 6k after your hp? I can't think of anything that should be 6k on a tank.
Yet struggle to tank in EC HM, seems I take a huge amount of damage from non-weapon attacks and the healer struggles to keep me alive.
If you're talking about Zorn or Stormcaller, there isn't anything you can do to decrease the incoming damage because they both deal I/E damage exclusively through F/T attacks. If you're dying, it's because your healer isn't doing something s/he should be doing. If you're dying on Zorn, make sure you're getting cleansed of the DoT and saving Resilience for Toth's jump and/or Zorn's channel stun. If you're dying on Stormcaller and not during or soon after Defensive Systems, it's a problem with your healer. If you're dying during Defensive Systems, make sure you don't break LoS with your healer and stay within range of them while you're kiting the rods and make sure your healer actually knows to heal you; you should be the only person taking appreciable damage during that phase so it should be relatively obvious. If you're dying just after Defensive Systems ends, it's generally because your healer is having to run to get back onto the tank while you're tanking the boss to the face and most healers (esp Sages) don't have particularly stellar mobile healing and often end up breaking LoS on you when they're jumping up. The solution I've found is to use Resilience after jumping back up on the tank: 5 seconds of immunity to all of Stormcaller's damage is a great way to buy your healer a window of time to get back on the tank and resume healing.
If you're having a rough time with Kephess, that's pretty much par for the course considering your gear. When you're actually tanking Kephess, it's important for your healers to know that pretty much the only person that's going to be taking appreciable amounts of damage is the tank currently tanking Kephess and they're going to be taking *a lot*. It's important they know this because, rather than just topping the tank off and looking elsewhere, they need to actually chain heal into the tank: even if the tank is fully healed *now*, by the time their heal finishes casting, the tank is likely to be at 50% hp. Kephess just swings and hits that hard. On your end, as a tank, it's important to learn when Kephess is going to drop his DoT on you and use Resilience to avoid it. The DoT *can* be healed through, but it's not necessary nor is it recommended, especially since you can just ignore it with Resilience.