Skills
Respecing early levels should be made very easy. It will allow players to try different skills, play styles before settling in on what feels good for them. Maybe set skill thresholds? Lvl 5, 10, 15. Once these thresholds are reached you cant drop below that skill level and you gain that amount of points to respect with. If you choose to replace the skill altogether it resets these thresholds.
You have given the player an amazing amount of choice on each skill, why make it hard for them to try this out early game?
Once you finish the storyline (hit the level cap that the devs want you to be) then remove this freedom. Not sure what this looks like but players should think about respecing. (I love D3 and played thousands of hours but it’s a joke when it comes to variety and flavour of character choice) Everyone is playing the meta builds set by bad Dev choices.
Masteries
Once chosen you should NOT be allowed to respec. Ever! Period! If you want to select another mastery than reroll a new char. I have played over 2000 hours in Grim Dawn simply because of this. It’s a fantastic feature and really forces you to think about what type of character you want this to be.
… or make this feature SUPER hard to achieve and a one-time feature. Being an ARPG, allow them to grind out a drop to forge something that resets your characters mastery. Make this super rare item have multiple uses as well. The whole point is to let player decide if they really want to respect their character or craft a BIS item.
You may be watching a stream or a youtube video of another player absolutely crushing the games content and think… hell yeah! I’m trying this build out! Don’t allow them to respect and grind an arena for a few hours to achieve this.
End thoughts
All this depends on how hard it is to get to end game builds and gear. If it only takes 5 hours to level a new character to put on the end game gear you farmed with your main then making things hard is pointless. Just re-roll. (D3)
however, if end game gear drops are very high levels and it takes weeks to level a new character to that point, then introduce another way for them to sink that time into. Give players choice and let them decide how they want to spend their time. (Grim Dawn/ D2)