I'm old. So take everything I say with a grain of salt because my experience tanking, and running an Axe tank as my main, is ancient.
Consider building with the full intent to respec in your late 30s, early 40s. END burn is painful at times, even with slotted stamina. If you're planning on scranking, soloing much, or considering passing on Taunt, you'll want those low tier, low END burning attacks in your chain as the KB/KD still shines in Beheader and Gash and whacking a mob in the face still works great to keep aggro through Gauntlet. As you get Swoop, Cleave, and some AoE in your chain in the higher levels, you've started managing END burn better and started to find some recharge love which relegates those low tier attacks to borderline useless. But they ARE useful in those early stages unless you like standing around spamming Brawl and Tranq Dart. Hence building to a respec, so you can be active in your aggro management and damage output in those low levels.
There's an argument to be had for Beheader if you plan to be aggressive in aggro management, even into late game. It fires FAST, so it's a great power for an active tank to "hop and pop" loose mobs. Aura maintains your herd, Taunt grabs your shooters/ranged mobs, and you can target a remote leaker or mob not within your Taunt range by targeting your leaker, "hopping" out of the pile with Beheader queued, "popping" that mob as soon as you're in range, them "hopping" back in the pile. 1 to 1.5 seconds, you clean up loose mobs, and your movement alone will often shifts shooters into melee, tightening the herd that much more.
Welcome to the best dang secondary in tanking! Good luck out there!