I do apologize if this has been mentioned before, but a quick search did not net me anything on the forums, so I thought I might mention (or simply reiterate) stipulations regarding this new helm tinker for those interested in it.
I'll let you form your own opinions, but before you put this on your helmet it's worth mentioning:
1) It looks like the old gnome MC helmet (metal cap with swirly hypnosis doohickey on front)
2) I did not see a bug fix for this (although it may have been fixed prior to live?), but even if you disable the "show helm" option, this helm still appears. If you die, occasionally it will hide it, but will reappear if you use it or if you die again. So it's a perminant look, if you want your helm shown or not... Again, this might have just been a bug on PTR....but also perhaps a design choice?
3) It's NOT a real MC. You won't be making anyone jump off cliffs. It's a CHARM effect, as if you're a hunter taming a beast. The person who is charmed will simply follow you around and you'll have a few very limited options (ie attack, stay, follow, etc)
4) A player can trinket out of the effect. In several days of testing on the PTR, every time I used it, the person trinketed out of it or it broke after a few seconds.
So as you can see, aside from an additional interrupt which might be usefull in BG (or off-chance/wiered PVE) situations (since it's not usable in arenas), this helm enchant is extremely limited at it's current 10 minute cooldown.
Boildown/personal opinion: Idea is nice on paper, but it's final iteration was severely disappointing. I'll be sticking with regular resil helm enchants for pvp. I'll probably put this on some crap helm just for fun every now and again, like if I see someone trinket, THEN I'd use it. Again... limited situational use, even with 45 sta. But since you can't change helms in combat... eh.
The other eng buffs, however, are awesome. Sorry if this is repeat information, but again I thought it might be worth mentioning to folks before they waste reagents on their primary helm if the preceding details are disappointing. Some of you might still thoroughly enjoy it, regardless. I hope you do more than I. =)