Best standard WAR opener as MT?

[Ditto]

Overpower is more initial threat, shorter range (the enmity modifier on OP is larger than Tomahawk, outweighing the potency difference, iirc). Pulling with either works since it's unlikely you'll be losing hate that early. A larger cushion is nice, though.

Anyway, the best opener is:

Infuriate -> Tomahawk/OP -> Brutal Swing -> Heavy Swing -> Unchained -> Maim -> Zerk -> Storm's Eye -> Internal Release -> HS -> SS -> BB -> Fracture -> HS -> IB -> Maim -> Storm's Eye -> Pacified

You should always be getting all of your buffs up first (Unchained + Zerk + IR + Maim + SE), then using BB to generate massive threat, IB for the mitigation/damage/threat, then reapplying SE before you get pacified. Fracture is only used if you have enough SS, but the 9 hits is the primary reason to reach the break point. You should never lose threat starting with SE (and buffs. no buffs = less threat = ya might get yoinked) unless you are severely outgeared, even with full VIT accessories.

After that point you can alternate between SE and SP, or use SE -> BB. Save Zerk to pair with Unchained unless you're out of Defiance when Zerk comes up. IR on CD. Keep Maim and SE up at all times. There ya go, WAR in a nutshell.

This, however I'd make a slight adjustment to the opener like this.

Infuriate -> Tomahawk/OP -> Brutal Swing -> Heavy Swing -> Unchained -> Maim -> Zerk -> Storm's Eye -> Internal Release -> HS -> SS -> BB -> Fracture -> HS -> Brutal Swing -> IB -> Maim -> Storm's Eye -> Pacified

Adding in the second Brutal Swing which chains into Inner Beast. (Brutal Swing is off GCD so skill speed wont matter there)

Also as Spooky said, to do this you would need enough Skill Speed, around 420/423 (Forget the exact amount) or so. Without that much you wont be able to fit in the last Storm's Eye, so you could either do that he said and cut out Fracture, or just deal with not being able to fit in that last Storm's Eye and wait until the pacification is up to finish it. It isn't really that big a deal, and sometimes it may be more worth fitting in that Fracture instead of the last storms due to Unchained still being up, and Fracture actually being worth using as the MT while unchained is up.

The pacify doesn't break your combo, and doesn't last long enough to make your combo expire, so it's really however you'd like to do it.