I wait for 14 to get Flow of Battle before Perilous, but this is how I've built my Lego 13 out of 15 times. The other 2 times I regretted it. (Though a case can be made for To the Death over War Cry/Payback.)
I absolutely love to see Red Templars when I'm on my Lego.
The times I've built To the Death, instead of Warcry (I can't give up Payback Strike, it's just too damn good) my party has died (mostly cuz I like to play with some melee dps in the group). After a bit, the boss (all 3) just does too much damage on aoe. I feel To the Death is just too dangerous given the obvious cool benefits, it comes with some heavy drawbacks that just aren't worth it.
You can build enough guard with WF, CS, and WC without it tanking bosses imho. Find a good choke point (door to zone 5), get your team in the room behind you, have your team lay down aoe and watch everything melt while you hold every enemy on your back. Definitely helps to have keeper barrier you when you need it, call for it when on cooldown. Vs Red Templar, pop WF when he spins, he's a big softie.
Definitely worth it to wait to level 14 to get Flow of Battle before going into Perilous, or if your team has another tank while you level up. Build order I tend to go with:
Guardian Tree straight down to get Walking Fortress and it's upgrade (level 6) and Warcry (without upgrade, level 7)
Combined Arms Tree to get Flow of Battle (level 10) and Counterstrike (level 14)
Then go nuts on Payback Strike's upgrade (15) Bear Mauls Wolves (16) Call to Arms (Warcry Upgrade at 17) Cutting Words (18) and then it's a toss up between Bulwark, Turn the Bolt, or Crippling Blows for the last level (19). No real reason to play at 20, just prestige and roll on! Now that my crit is a bit higher, I'm going with Crippling Blows and there's a noticeable difference in the damage I take at level 19.
Hope you guys are building fantastic tanks and helping your party own in MP! I never really liked playing a tank (too much time tanking in WoW, and in this MP, Assassin and Necromancer are my fav classes) but grouping with some terrible pugs with terrible tanks prompted me to play a lot more Legionnaire, and I'm absolutely loving it.