100% with you on clarity and precise language, although I think you may underestimate the amount of work that would need to go into it---there are about 700 item enchants and 300 unique passives alone, many of which are not easy to pull apart. (I still think it's worth it, regardless of the time involved.)

As far as the design choice in how constructs interact, again I agree, but we've definitely had that discussion with the devs. The reality is that ship sailed a while ago, and the decision is baked pretty deeply into the game. That said, I think you may be overstating the penalty TA's get. One thing to consider is that 40K Inquisitor heavily weights gear choices over skilltree choices. Perks are strong (and TA has a variety of powerful unique ones), but passives are generally not. TA gear, moreso after the recent 2.3 patch, has a lot of options for construct-focused builds. Additionally, consider the prospect of allowing all passives and skills to benefit the TA *and* constructs: you now have a class that double-dips heavily in most stats. Finally, remember that TA's have a whole extra interface over crusaders and assassins (pyskers have their own) in addition to a slew of unique item types (construct equipment) and several skill trees. As far as "customization", a lot of that is over on that side.

I'm not really trying to convince you that the status quo was the right choice. I'm mostly just trying to offer another perspective to help you avoid feeling like the TA is fundamentally broken. Don't get me wrong: the Tech Adept is, overall, generally weaker than its counterparts and in need of buffs. But there's a lot of room to play around, customize, and regain balance even without rebuilding the class mechanics from the ground up.

One last note: while I agree that the interface could really use some clarity and consistency, most of what I was mentioning isn't really guessing. The game data files are not encrypted (they are packaged, but easily extracted), and the skill mechanics are available to inspect. For many item enchants, there's literally a "MinionEnchant" flag that forces it to apply to constructs instead of the player. That doesn't help the *player* much at all, but it does give us some ground truth as to how things work.

As to perks If it's not written that it affects construct's it does not. Same goes for skill trees. Only Construct skill trees affect them. Other that that you can affect your constructs by decreasing cooldowns or applying statuses on enemies that increase construct damage (vulnerabilities, burn,slow,stun etc).

Season of Inferno also added gear specifically targeting buffing constructs. Prefixes are marked in blue (word Constructs or specific type of construct is in blue)

As to psalm doctrines only two affect construct directly +50 Construct HP / +50% Construct DMG

To be honest before Season of Inferno it was much worse to make anything worthwhile using constructs. Right now with the new prefixes you actually can make something out of it. 

A good rule of thumb is "if it doesn't say it affects constructs, it doesn't affect constructs".

Psalm doctrines generally do not affect constructs. The +50% heat damage doctrine does not affect constructs. The ranged and critical skill trees do not affect constructs. (Also, constructs cannot crit.)

Debuffs on enemies do generally affect constructs, for instance vulnerability stacks and slow/stun/shock/etc. I say "generally" because a few passive skills that are written as "enemies do less damage" are actually implemented as buffs to the player (and not to constructs).

I'm not suggesting that this is the right or wrong way to implement skills (okay, maybe I'm suggesting that writing descriptions which reflect the player-buff/enemy-debuff behavior correctly is the right way), but it's a lot more cut and dry than I think you're assuming it is.

Hope that helps!