[{quoted}](name=IH DeamonDragon,realm=NA,application-id=3ErqAdtq,discussion-id=d6FiBbau,comment-id=0006,timestamp=2017-03-17T13:59:53.827+0000)
Tahm is good with a lot of health and, against a Brand, MR is your friend. Banshees Veil is a good buy against Brand for the passive shield. Locket will also give you to MR and an active shield to defend with. I'm also assuming you're starting with Relic Shield as your gold item, so upgrade that into Face of the Mountain for more shielding. Do not forget to use these actives. If their team has other mages aside from Brand also grab a Spirit Visage. I would highly recommend switching your keystone to Stoneborn Pact, and when it procs ping the opponent for the ADC to attack so you can make the most of it. Hide behind minions when you can to avoid the stun and dodge his W the best you can. There's not much you can do about the burn. Try to keep your team from clustering together, it makes his ult devastating. Like some others have already said, Tahm is not a great matchup against Brand. This is mostly because of his passive which (according to the LoL site) deals 2% of max health damage for 4 seconds and is super difficult to avoid especially with his E being a point and click.
Personally, I avoid playing tanks against Brand. My most successes playing against him have been with Nami.
I did switch to stoneborn pact but its pretty useless...after a 
dashed towards my 
I slowed him with tongue lash and applied stoneborn but didnt auto attack back...even when I pinged and typed in chat... instead she hits the enemy minions and rarely hits on accident with her arrow volley spell multi target spread thingy...
Maybe when adcs learn how stoneborn pact works or atleast learn how to retaliate during a trade...then it will be decent.
And yes I have been getting locket whenever I see brand on the enemy team....sometimes paired with merc treads depending on the rest of the comp..but it feels like he really out damages the active even when timed right...plus his cooldowns feel very low.......
And banshees veil feels pretty selfish on a tahm support.. i tried it and it doesnt really help since you have no mobility burst damage or hard burst cc (strong/hard cc that can be landed instantly...) so there really is no reason to tank a single spell that could have been an aoe..its not like tahm kench is an important target.....and his potential to do any form of his single target hard cc requires a long fight...one that banshees does not support ... but merc treads sorta does..
, even when I catch him at melee range he manages to stun me before I can auto q auto.... and even when I chain slow him with q his stun is just a better cc.. and its always back up...getting 3 stacks on him to land my own stun is nearly impossible...worst of all is he is aoe/multi target....I mean I can shut down his ult by eating someone to stop it from bouncing sometimes but his stun has a lower cd then my w and even lasts longer then my q 3 stack stun.
into 
i was 2/9/27 and enemy brand was 2/12/22... he didnt even have wards and when we lost the enemy team says gg ez and that I suck CLEARLY BY THAT LOGIC TAHM KENCH IS A GOOD LATE GAME CHAMP AND I DID SOMETHING WRONG? I saved teammates so many times yet I am told that I suck by the enemy brand and then he leaves....clearly support is just a trash role that gets no respect for anything or I just cant support...
and pray. otherwise try and bait out his pillars. you'll be more of a babysitter then a engager that game but you can still make a difference.