Take a look at the values in the OP again Kitru, the tech tanks have an unusually high optimal shield, an average absorb, and a very low defense value as their sweet spots.
The most you would need to do, assuming you're not using the passive stat relics, is 4-5 (full 27 unlettered mods, full Bastion/Bulwark enhancements, and high mitigation ear and implants provides you with 600 Shield exactly, with a stat budget of 1648 without using passive relics). I've also got a bit of a problem with using those exact numbers because their interplay with the various relics and debuffs: the presence of the acc debuffs, especially the 20% from Smoke Grenade, is gonna do some wonky things to those numbers when factored in (especially when factored in when weighed based on uptime rather than averaged for effect). It's one of the reasons why, even though I know about these calcs and think they're a respectable guideline, I don't follow them explicitly (my Shadow optimal loadout is 532/600/516 rather than the 500/525/600 that I "should" be aiming for).
Note: I forgot the numbers and source, but I remember someone worked or the 4 piece set bonus for jugs as being one of the best in game, will try to dig it up later or do independent math. I wouldn't touch the tech tank bonus.
The reason why it's so awesome is the same reason why self healing is so awesome for Shadows: it's post mitigation flat damage reduction. Post mitigation incoming damage is low enough thanks to high tank mitigation that the comparatively minute increases to abs/sec equate to truly impressive decreases to required healing, especially for the hybrid spec which gets 25% more out of it.
I do find it amusing that the 4 pc set bonuses for VGs and Shadows are designed to offset the weakest point of mitigation (Defense for VGs; DR for Shadows) whereas Guardians just get an outright improvement to an already potent mitigation mechanism.