It doesn't work that way. THF's evasion rating is A+ which means it caps at 361 @ Lv90. WHM's evasion rating is E, the worst of any job in the game, which means it caps at 255 @ Lv90. WHM has its share of evasion gear, off the top of my head:
However, even this is not going to come close to covering the ground between 255 skill and 361 skill, let alone all the evasion THF can stack on top of their native skill using their own evasion equipment. Blink is also much less reliable than Utsusemi.
Using Utsusemi, you can blink tank as a WHM. That works decently, but you won't be getting missed very much. Pretty much every single swing the enemy takes will eat one of your shadows. That's not to say it can't be done, I've tanked some fairly hard stuff on WHM/NIN, but it's a far cry from what you'd call an 'evasion tank.'
I honestly think you'd be better served by going after a spell interruption -102% build which would ensure complete immunity from interruption. That way all you have to do is keep your MP high enough to cure-bomb yourself. In my experience, this is the best way for a WHM to survive tanking.
____________________________Pergatory (Asura, Kupo LS) WHM99 ~ SMN99 ~ DRK99 "If you want to know me, look inside your heart." -Lao Tzu