If your Diablo 4 won't be locked behind a huge virtual paywall.
Respeccing was relatively easy in the Diablo 4 beta, and required little to no gold to do so. Things will get more and more expensive as you grow in power and build out your character, but the devs have promised that, even at the upper levels, reworking your abilities isn't a massive coin sink.
When asked if the respecc system is "for sure going to ship in the launch," Fergusson replies "it's not prohibitively expensive and we've made it easier by being able to refund a single skill point or the entire tree at once."
Given that my playthrough on the Necromancer was very much trial and error, I found myself having to respec quite a few times. It didn't burn a hole in my virtual wallet, nor was it an arduous process of having to rebuild the entire tree – as Fergusson alludes to, I just removed the specific abilities that weren't quite working for me.
It's a really great system for those who are new to Diablo, as well as us veteran theorycrafters who spend way too many hours trying to maximise their character's potential. It's yet another leaf out of WoW's book, and while it's seemingly quite a minor feature, it makes all the difference.
With the games like Diablo to quell your thirst for blood.