There is a problem with not making it nobuild. Its a little known fact (as far as I know) that since the spyper update spies can take enemy teleports.. meaning that they can get behind visualisers if an engie decides to grief..
but that does need griefers, and they're dicks anyhow so I dunno.. opinions?
Not necessarily.
Make a second noentry at the actual spawn gate. Tada. Now a spy could take the enemy teleporter, but at most grief the little "hall" outside.
As for problems with Hoodoo... I'll be honest, it's a beautiful but very unbalanced map. It seems you were going for aesthetic over functionality. Well, overall it's a very "closed" map, so my first critic goes to the actual design. Tight linear corridors favor the heavier classes and sentries immensely. I've once held countless waves of enemies almost alone as an heavy in stage 3. The only backup I had was a medic with Kritz (and he died a lot) and the odd red who'd stroll by like a lemming, run off, get killed, respawn after 12 seconds. Every Kritz I'd clear up the entire enemy team cause they had no place to run to. My "streak" finally ended around the third time I finally ran out of ammo.
The first map is the best of all Hoodoos, for all it's "tightness" it starts out pretty open and has a few alternative routes, so all in all, the most balanced. The only problem being how easy it is to get spawn camped right off the bat...
But then at stages 2 and 3 shit hits the fan, hyperdrive mode.
IF you don't get flooded right off the bat in stage 2 (as mentioned above, really should be blocked by "noentry"s) and spawn camped for around a minute, the first part is pretty much a breeze, getting the second spot, on the other hand, is sheer insanity if the other team is at least competent.
First you have that infernal ledge, easy to "nest" to hell and back. 2 or 3 engies stacked there + a heavy (or demo, or pyro, or whatever really since more often than not there'll be an equal number of teleports up there so it'll be constantly "full") can keep an entire team at bay. Spies seldom have a chance against entire nests, specially nests with extra backup of classes constantly spamming (dispensers will provide infinite ammo there). A single uber will not only get stopped a lot on it's way to them by enemies but will also get knocked back against the wall of the tiny ramp which is the only way to get up there, and instantly killed as soon as the uber runs out. The end result is that it takes at least 2 very good ubers or 3 normal ubers to actually take out the bloody nest. There's no other way up there. The "window slot" that you can lob grenades into is too small to allow you to clear anything, and, off course, a suicidal pyro (or demo, or soldier) later and off to start with you. It's a very short dash from their teleport up there into your face.
So basically, huge choke point right before point 1.
How to fix it? Several people have mentioned options. Providing additional means to get to that bloody ledge would help (some guy had a pretty good idea, even did some diagrams and such). Making the window bigger so you can clear a bigger area by lobbing windows/rocket jumping and shooting would also go a long way.
But after that one there's another. Point 2 is no less of a giant pain. You can pretty much place sentries anywhere under the "mine" ledges because a single sentry (let alone two) behind the "rock" left of the tunnel exit is downright unreachable. It fires into the mine as soon as you open the door, so there's really no use for that tunnel. Once you remove that tunnel your options come down to the huge choke point. An extra sentry or two, and the entire rest of your team will provide enough power to hold that.
How to fix that one? First either get something behind that rock so people can't build a sentry there, or make it a bit "deeper" in, so a sentry there can't outreach people just opening the door in the tunnel. That one's just mandatory, because as long as that sentry can singlehandedly block the whole mine, that door might as well not open.
After you make sure someone can actually open that door without being met by heavy sentry fire, I'd suggest taking the tip previously mentioned in giving people additional routes to the mine tunnel.
As for stage 3... Well, the whole thing has 2 problems for both teams: For red it has no good sentry spots except the last one, which is ridiculously overpowered... Ironically. For blue, the whole map is really tight, and, I'm not sure here considering I rarely play stage 3, does that damn red "first" gate stay open for how long? It's a major pain in the ass to be hit from behind with no real way to defend yourself and breaks flow a lot. Honestly don't see the point of that gate, it could justify not forcing red team to go a mile around to defend the first point, but there's another opening a little further ahead if I remember correctly... This one just seems to serve to "backwhack" the cart every other minute...
So major things to fix here would be to remove that gate at the start, and open up the little "house" at the ending, that basically houses a million and two sentries you can't shoot at without getting in their range.
That's pretty much what I can remember off the top of my head.
PS: Don't cater to the "instant respawn" servers, they suck and deserve all the unbalance they get. Any half-decent defense is downright unbreakable on "instant respawn" servers. The problem with Hoodoo, on the other hand, isn't instant respawn, it's the actual design.