So because not every piece completely replaces old choices it was a backwards design choice? The body has 7 triple attack on it. There is nothing else in the game that competes with that. On any content that actually matters, your attack is incredibly unlikely to be any issue whatsoever. I truly do not understand how you aren't happy about some exceptional gear upgrades.
Because it's not an exceptional gear upgrade at all. It would be palatable yet confusing if it was an upgrade on it's own but after seeing the stuff all of the other jobs get it's clearly one of the weakest sets because it halfasses trying to be everything instead of actually being good at something.
Assuming you have proper amounts of haste since capped haste is available on 99% of content:
Hat is on par with the hats the other jobs have by some miracle.
Body has triple but now you lose out on DW. Still actually pretty good. Not obscene like some of the other slots but still an upgrade once utilized properly.
Hands are DW for a TA piece aka a detriment and are actually WEAKER than Ambuscakdi+1 on WS. Unless SE altered how the TA augment works then the TA aug is nigh useless due to it's place in the formulae. They might be able to slot in for adhemar instead to cover for the loss of DW in body when you get the +3 body. Due to this it's generally a good idea to look at body + gloves as a pair if using for TP in high acc situations.
This makes you lose at least 6 stp on the Nqs alone and your overall triple attack goes up by a massive 1% when you were already 40%+.
Now of course there are other options like dropping an earring for Suppa which would mean there's no use for hands on TP except to make things worse.
Legs gave some ta and crit% but they're weak enough that people here already question whether to use them and Lustratio+1 are still probably king on ws.
Feet are entirely for the movement speed and magic eva because noone gives a hoothoot about a second or two more of flee. They're inferior to lustratio+1 which will give a set bonus with the legs to make the crit+ dmg on the omen legs obsolete when compared as a set.
Then about half of this nonsense I typed goes out the window if you had any luck during a dark matter campaign and got misc combination like QA STP DA and/or WSDMG 8 augments in the wrong slot.
Now there is still hope for the omen gear having aug sweet augment paths but that is irrelevant to your overall argument about how amazingly awesome thf set must be since the reason thieves are disappointed/upset in this is that the sets are inferior in terms of how much they were upgraded compared to some other random job's omen sets they checked out before augments even came into play or were discovered.
If you had some herc gear and then went to solo some reisen NMs you'd have had more than enough stones for the lotto to do a roughly better/equal job than most of the thf set in certain roles via the magic of gearswapping and having the patience to sit down at the npc.