Mongoose? Executioner? Meh. Executioner may help dmg and mongoose may help speed and dodge for a few seconds, but I'd promote a better choice for tanking, and as soon as I have enough money for the mats I'm getting it: Battlemaster. Just like Felsteel Helm plans, it may be hard to find, but the heal that it gets in to all nearby party members not only helps with the agro portion, but it helps with the healing aspect of instances/raids as well. I off-tanked next to someone who had it on his sword once and it proc'd more than my mongoose.
That's not likely, testing happened when Battlemaster first was released it and procs next to never, unless they changed it. Also overhealing doesn't provide any threat, and it heals for like... nothing. and healing aggro is 2 healing = 1 threat. so assuming it heals for 100 to your party, that's 250 threat, for a proc that happens once in a blue moon, and if any of that healing is overhealing it goes down. It's lackluster. And 100 healing ISNT gonna help your raid much at all.