How are you forced to use the respec system? Do the devs force you to use it? Does not using it mean that you will not get punished for using an obvious bad build? Will the minions of hell take it easy on you because you have a bad build, just because you have a respec system in place? What prevents you from making the choice to reroll? Does this game only allow one character per class?
In all Diablo games your not as much forced to respec to make a viable build, you are forced to grind and search for items in the highest difficulty area you can manage. Improve your gear is what gets you further on, and a few levels might do a little. But no, dev are not forcing me to do anything, they are forcing me on a standard build where I can just choose some different ways to attack and something i can wear.
Your first playthrough will consist of what you gain and what you find, nothing else, and in D3 you just gain a standard hero, then you can choose some nice ways to attack or som buffs (skills), and you have to make the best of whatever you happend to find. Then you can start grind and search for some specific items too boost you in a certain "specialization", but beneath all that, they're just the same. I find that a bit boring and uninteresting - if you so much like auto-spec, just have a option to just auto-level for you, you seem to like that.
You can still specialize, until I see the skill/rune changes this is a build that I intended to take through on my first playthrough. A barbarian that uses slow, as his primary damage mitigation http://us.battle.net/d3/en/calculator/barbarian#aZcbWk!YcS!bcbYYZ. So he would specialize in slowing down the mobs. Sure I would need gear that would help him survive by adding in other forms of damage mitigation.
You "specialize" around gear and some skills with a particular affix "slow", that could just as easily be done in D2.. I'd rather specialize in the way my character treats incoming damage, or favors damage output versus input.. I just don't see why I can't have the full control of that aspect instead of just some sockets.
Someone that is good at math could tell you just how many point spending options existed in D2. I am not that good at math though, then they could show you out of those options how many are hell viable. Which means how many could be used to solo hell with. Where as with D3 I am certain that there will be way more viable builds in inferno.
As mentioned all the melee characters can do hell with no skills set (they just makes it easier), so in regards of amazon, barbarian and paladin, you're looking at a something like 110 in the power of 30, with some limits (due to max 20 points being allocated in one skill), then you can multiply that by somewhere around 100 for different ways to distribution of stats (cuz you won't have full control, but estimate around a 100 different ways) - when it comes to the caster characters you have 505 in the power of 4 different ways to use stats, but a limited way to spend the skill points cuz you need to specialize, but they have 5 different skills which can be used if maxed to level 20 and then you can dump the rest as you want, so lets just say that you have a 70 in the power of 25 different ways to use skills.
You're not limited to cookie cutter's or maximum builds if you are to beat hell, just the right eq and you can basicly do it.
D3 on the other hand has ~24 skills which you can use to fill 6 slots, thats 24x23x22x21x20x19x18 or somthing like that, and then you can choose 6 runes in each, so you can rasie that in the power of 6. Then you can multiply that with the number of different ways to select 3 different passives. most characters have 16 passive skills (except monk) but only a few of them would actually benefit your skills and the way you runed them - from what's expected of Inferno, you most likely need those buffs so that limits your choice to maybe 8 different passives to fill 3 slots, giving 8x7x6 ways to select those, and then you can multiply those to numbers and get a fair estimated, with a 5% significance