Well, I'd give a more responsive... response, except there is a lot of wall of text above me that I'm currently too lazy to read. My fault for being lazy.

I'll give my thoughts about it then.

One issue was the time between OVA2 and OVA3. This meant undue hype that, no matter how good OVA3 was, made it difficult to live up to. But that's for long time Tenchi Fans. Newers ones? Well... while I like OVA3...
1. The execution of story was poor
Over all, I will say I was disappointed with OVA 3 story execution. But I don't hate it. I just thought that it held a lot of potential that, because of length restrictions (not, at least less, the fault of Kajishima and more the limited budget and limited amount of episodes he was given), just didn't feel right flow wise. For me, the first 5 episodes of so, which had flashback, info dump, and the introduction (at least for the anime) of Mihoshi's brother and love interest antics felt, filleresque I guess. The info dump part might have been a necessity given again, the limited amount of time he had to work with. But that's stuff that, IMO, works better either drawn out in a visual medium, or something that is better as a novel. I was especially disappointed with the Choushin War since it was, for all intent and purpose, relegated to only one episode. While the antics of the brother got a few more.
Again, I don't blame Kajishima, but what he was forced to work with. Ichiban Ushiro no Daimaou suffered the same problem. Tons of awesome story perfect for 24-26 episodes... crammed into 13 instead with side OVAs at the end (which never got finished because the company making the anime went under. But that's another series talk for another day~).
2. the added characters are useless
I admit, I'm one of those people that got annoyed that it wasn't the Kiyone we knew. But Noike instead. The first time I heard about her. However, older, more educated, I now realize she's an integral part of the OVA timeline that, and this is again another slash against Western fans of Tenchi Muyo, were unable to realize since we don't get the True Tenchi Novels here.
Mihoushi's brother (even forgot the name.

) I kind of saw less reason to dedicate the number of episodes for him. But at the same time, didn't think he was useless per say. I may have preferred a more side story role for him in like, maybe a manga or a spinoff OVA instead of it being in the big 'OVA 3' series. But I have nothing against him generally speaking.
The other characters were seen if you have watched GXP. And you could say were developed in that series. Which again, hurts WESTERN Tenchi Muyo fan's discovery of Noike since, while you do get her back story, it might have felt to most WESTERN fans that this somehow an ass pull to get a new character in the show. That 'usurps' the mainstays. Again, due to things like not having the True Tenchi Novels translated and these Tenchi Muyo fans being 'casuals' that only watched the anime. Probably not realizing that Tenchi Universe or those movies aren't a part of that timeline.

3. the new developments( Tenchi being a god, Washu being a goddess, etc.) make no sense
Tenchi Muyo to me was always a complicated series. Even more I discovered websites that explained, or tried to explain all the connections and theories. Though I can understand casual fans that want things simple and easy to understand packages not liking it. Well, I'm not one of them.
4. It changed things established earlier
I guess I can see where someone could say that. But since I've always known the series to be a huge complex universe, it didn't occur to me that something might have 'changed'.
So in conclusion... OVA 3 was still good series. Flawed? Yes. Good as the first two OVAs? Nope even if I take off my Nostalgia glasses and try to judge the first two with today's standards, would still go with the first two. But my complaints isn't so much rage that OVA 3 gets in these 'debates', but more disappointment. However, just seeing the characters again and in that timeline still makes me squeal like a little girl. And I'd be there Day 1 if OVA 4 was ever made.