The aggro bonus of a single TF proc comes down to 240 (debuff bonuses) + 270 damage done in DEF stance (usually completely unmitigated though sometimes resisted). Thats 510 Aggro without aggro modifiers of DEF stance and Defiance.
Heavy Devastate spam resulted in more that 11 procs a minute. Though this was done on a lvl lower mob and without using shield slam (which does NOT proc TF anylonger).
A 50 damage delta on the weapon range (of above linked sword in comparison to TF) results in additional autoattack and devastate damage. All other moves when tanking are unaffected by the weapon change (neglecting HS here but the speed difference of TF and said sword is minor in this respect). When sonsidering parry, dodge and miss rates, even with a high crit rate in buffed tanking gear the DMG factor (crit/hit/dodge/parry) the "nominal" damage on averge hits the mob should not exceed 1.2
This is neglecting glancing blows (which favour TF), blocks (which favour higher hitting weapons) and AC mitigation (which varies from mob to mob but favours TF).
At 1.6 speed this 50 damage range surplus translates to 60/1.6*50*1.2 = 2250 additional white damage.
And 50/2*25*1.2 = 1500 additional devastate damage (going by 25 devastates done in a minute, which is not unreasonable when considering revenge and shieldslam and shouts).
So we have 3750 additional aggro on a mob with 0 AC mitigation.
"Just" 7 procs a minute of TF make up for this. This is not unreasonable.
This is for single mob tanking only.
WW and Cleaves heavily favour higher hitting weapons.
While WW and cleave do favour harder hitting weapons, remember that TF can proc off each hit of a whirlwind or cleave. Of course, on many bosses (on live and in beta) aggro is not an issue, and you revert to using whichever weapon has the best mitigation on it. Assuming there is another TF in the raid, or a warrior with imp TC.