Ok I dont think you really understand whats going on here. Lucid is entirely right about this. A golem mancer isnt a tank. Its golems are the tanks. Since clay golems slow the effected monster; reducing the number of spells and attacks it throws out and are incredibly tanky, they allow you to tank difficult bosses very easily. (if it weren't for clay golems, lich king items would be much rarer) The necro itself, just needs to cast the appropriate curse and then hide in the corner. That makes it a strong and (more importantly for a reset) cheap support character. So early on in a ladder reset, there is no better support character than a golemancer vs bosses.
As for the DPS role, currently the javazon is the best overall DPS character in the game. Its just very hard to gear so you dont see many of them. It has the highest single-target dps with charged strike. (Charged strike does more damage then zeal and doesnt have an attack rating, it also does more damage than smiters at perfect gear) Its aoe is almost as good as the bowzons as well. Where it loses to the zealers is in areas like plaguelands and inferno areas, where the monsters arent clumped enough for lightning fury to be effective and their hitboxes are too small for charged strike to one-shot them. In those areas, its lack of sustain hurts as well.
The best DPS role for a ladder reset is up for debate now. I havent tested this, but I think an orb sorc may be able to compete with the javazon now vs bosses. Its super cheap to gear, and a skilled orber has high single target damage. Its also safer than a javazon at that stage and the change to cold mastery means it doesnt care about immunes anymore. At a ladder reset, I may suggest a orb sorc over a javzon in some scenarios. A good sorc can dodge sindragosas much easier than a javzon can for example. There may be others that are competitive now with the change to immunities that I havent thought of. I would be curious what others thought about this.
As for your larger concern about the item curve. Before this most recent patch, I would have agreed with you that the curve was too steep. For basically every character, it was basically a tale of two lives: life before cowset and life after cowset. The only characters whose best-in-slot items did not include cowset were basically builds who used the shrieking lich and glass-cannon bowzons. I cant think of any others.
I dont think its sunk in for a lot of people yet. But that has now changed. It is now the case that rares are the best-in-slot items for most slots since they have the potential to roll better than any unique that doesnt have a build-defining proc or spell-effect. So rares can be extremely powerful now at the very end game. In addition, they can be very strong early on. Even the low-medium rares can be very effective for people without much wealth early in a season. They allow you to farm content effectively until you can get even better rares or those build-defining uniques you need to complete your builds. You just need to be able to determine what stats your character needs and hunt for rares accordingly. This is something anyone with a working knowledge of Diablo 2 can do. If you need help on what stats you need for what builds, well thats what the forums are for. Plenty of people around here (myself included) will be happy to help you with these things.
Happy Hunting