Again, its going to give grevious wounds and negate most of yi`s healing, meanwhile most tanks have decent enough base damage to be able to synergize with magic pen, especially when they cant really abuse the basic attack % reduction from tabi all of the time.
As for tabi vs sorcerer shoes
20 armor out of 170 armor is a lot less than 18 magic pen out of 70 mr
I just went sorcery shoes and carried, while tahm kench is not exactly a tank, he most certainly is on that side of the spectrum...
Sorcery shoes wasn't bad when I tested it on malphite either, or amumu, or nunu zac sejuani galio etc.
Only time I really felt it was iffy was on maokai since he does very little damage compared to the other tanks and relies on consistent healing with his passive (so he really cant let himself be bursted in order to function)
Im not telling you to build sorcery shoes on tanks nonstop, im asking you to consider them when the enemy team does not do much damage via basic attacks.
Thornmail + sorcery shoes isn't supposed to be a net gain vs whatever master yi can build (unless its against a healing item) its there to consistently and considerably damage him..
Ill give you the benefit of assuming master yi has somehow obtained 70% magic damage reduction (200 or so mr), 13 damage to him per auto. At most.
He autos you, autos you again for a double strike, that's 13 x 3 =39 damage, autos you again, procs rageblade and then procs his double strike for another 13 x 2 = 26 damage.
26 + 39 = 65 damage over the span of 5 onhit procs which realistically can be done within a second...
You also have 70% magic damage reduction (a lot more possible as a tank), instead of his
dealing 80 damage it deals 24 and heals for 24 when under half health.
Then your grevious wounds apply, reducing healing by 40%.
24 x 0.6 = 14.4
So instead of healing for 80 per hit he heals for 1.4 (after subtracting 13 from
) And all other healing is reduced by 40%.
AND THATS IF HE SOMEHOW GOT ENOUGH MAGIC RESIST TO TAKE ONLY 30% MAGIC DAMAGE.
OVER 200 MR!!!!!!!!!!!!!!!!!!!!!!!