So, tenacity's defense/HP increases are not going to be what saves a player from a tankbuster. If a player is relying on that, they are doing it wrong. For the content where melds matter... more defense/HP is not going to help. There are DPS checks. Melds have to be DPS-focused just based on how the game is designed. Therefore, they can either leave tenacity in the game and it will simply be rarely purchased and melded to gear. Or they can abandon it entirely and just put Direct Hit on tank gear.