Sturdiness and Immunity Enhancements

I'm looking to optimize my tank gear, and I'm wondering what's actually in game and what's not. Here's my thought process: a BiS enhancement for a tank has the most mitigation points on it. High endurance is 2nd to D+S+A. Currently, from Askmrrobot.com, the list of these looks like this:

• Advanced Sturdiness 26 - 98 (57 S + 41 A)
• Advanced Immunity 26 - 93 (57 S + 36 D)
• Advanced Sturdiness 25 - 88 (51 S + 37 A)
• Advanced Immunity 25 - 84 (51 S + 33 D)
• Advanced Sturdiness 24 - 82 (48 S + 34 A)
• Advanced [mod] 26 - 79 (57 S + 22 A/D)

Are any of these (aside from the Steadfast and Bulwark 26) in game whatsoever? Has anyone learned the schematic? Since there do not seem to be any 26 enhancements attainable by themselves (as drops) I am pretty sure the top 2 aren't in. I'm guessing that the other 3 might be dropped in EV/KP, but they could also just be red herrings.