I like the direction of Tahm Kench changes on PBE, but...
What are these changes attempting to accomplish? Keep in mind that he has a ~44% win rate as support and ~46% win rate as top laner in plat+.
"But his passive deals TOTAL health damage now!..." - Remember that you will have to auto attack someone 3 times in order to get the most out of your abilities. That means you are guaranteed to do 6% of your total health to the target before any other damage. This means more early game damage for trading, but lower overall poke damage. It seems like they are trending towards all-in engages where you soak up most of the damage and pop your shield for extra effective HP.
"His shield is stronger" - Technically, yes, but notice that it is now only 70-90% of total damage taken instead of 100%. The duration reduction doesn't bother me because the shield does not decay. You lose probably 2/3 of it to decay anyway. Maybe the idea is here that you can level it if you are against a harass lane and self-sustain a little better? The return health buff is welcome but mostly aesthetic - since this skill is usually leveled last, I never really notice the 20% health return.
I will say that I am glad they are giving him an actual, interactive passive. But that then begs the question as to how weak his ultimate will become. His ultimate is now only a very slow teleport+1. Not useful for much more than returning to lane or pushing another lane. It would be nice if they would decrease the travel time, even just a little bit, or increase the range at earlier levels to compensate for such a slow travel time. They did reduce cast time by .5 seconds. Suffice it to say, his ultimate does not 'feel' ultimate.
EDIT: I just realized that since Tahm does not convert ALL of his damage taken into grey health, the actual health returned (which is based on how much grey health Tahm has accrued) is significantly less than before, since you used to get (at level 1) 20% of all grey health (which was 100% of damage taken). Now, you get 25% of 70%, which is significantly less than before. Its actually a sizable nerf to his sustain.