You can't do Taunt>AoE Taunt>Taunt without having a break in the duration of the taunt debuff on the boss. Taunt is on a 15 sec CD so, at best, you'll have a 3 sec period where you're not the focus of the boss while your ST taunt comes off of CD.
As to the OP, tanks should always tank on the inside platforms closer to the boss (I do 10 until the first tentacles die and then 11 for the second pair and back on 10 for the third pair; DPS should know not to leap to a tank's platform to avoid Slams) because said attacks are M/R rather than F/T. If you're on the outside platforms, you're gonna have a bad time from all of that unmitigatable F/T damage.
Yeh, I do taunt wait 7-8 secs then aoe taunt then taunt again when its on CD. 1-2 sec of random DPS/heals damange is better than the whole 15 seconds of DPS/Heal damage. I find that Our dps take care of the fight in that time, and if not, the other tank has his taunts ready.