Well, there's several schools of thought on how to make a tough Fire tanker.
In this thread, Baelrath is has made a somewhat novel build focused on defense. You could just slot your /Axe attacks roughly like he's slotted his /Fire attacks and you'd do well.
I myself lean toward somewhat more conventionally four-slotting the defensive toggles -- Reactive Armors if you're going for defense, Impervium Armors to improve your endurance issue, or even Impervious Skins 5-slotted if you're going for recharge (more on that later).
Kinetic Combat (very expensive) or Smashing Haymaker in single-target melee attacks will help with the smashing/lethal defense, which will be by far the biggest payoff in typed defense slotting.
Or you could go for positional defense, since Fire starts with zero of either type.
There's an alternative line of thought to defense -- see Coldmed's post here. Let Tough and your primary toggles keep damage within the ability of Healing Flames to fix, and concentrate on recharge and endurance and use your damage output to "outkill" the enemy.
Use this page as your bible when planning builds. Click on an individual set's page and at the very bottom you'll see tags like "Sets that improve melee defense," or "Sets that improve recharge," and so on. Try clicking those to get summaries of all sets in that category. You can sort those tables (click the arrows in the upper right) to see things like which ones give the highest bonus, which ones use the least slots, and so on.
If we are to die, let us die like men. -- Patrick Cleburne
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The rule is that they must be loved. --Jayne Fynes-Clinton, Death of an Abandoned Dog
I recently started using Energy Torrent from Power Mastery to help keep mobs on their backsides, and much to my surprise it works very well. This would mesh well with BA's KD and Burn if you're using it. Power Master also offers Conserve Power and now Physical Perfection (I think that's what it's called...) which will gives you two more End management tools. Otherwise You'll have to invest in some IOs to help you out. (Numina's, Impervious Armor, Gift o' the Ancients, etc...).
Tanker Tuesdays: Meet in King's Row by IP Gate 6pm PT9pm ET.
1st Tuesday on Champion, 2nd Tuesday on Justice
3rd Tuesdays (Odd months) Freedom, (Even months) Virtue, 4th Tuesday, Tour, Server TBA
Brutal Thrashing Thursdays: Justice (ask Papa Slade when),meet in RWZ 6pm PT9pm ET.
So I've had no luck with the search function on these new boards and I've now scanned through 30 pages without a single post with FA/Axe builds or guides. I'm beginning to think I might be the only one of my kind out there. In a world of Stone and Shield tankers, I'm looking to toughen up my level 41 Fire/Axer Cherokee Sun. I solo alot, but don't mind grouping if I can find one, I've never PvP'ed. I've found myself heavily laden with endurance problems, and every build I come up with I run out of slots. I also really need to step it up a notch and add some defense to help my surviveability, how close to the softcap is reasonable to stack with my resists, without spending a ton on the build?
Please, any help would be greatly appreciated. I want to love this toon and get back into playing him, but it's a tough road.