This isn't a very good system because it doesn't improve gameplay in any way, shape, or form. All it does is slightly decrease difficulty over time by giving you stats. This is a feature that targets achievement oriented players rather than gameplay oriented players, however in order for achievements to be worth anything, they have to establish some solid gameplay so that there is a player-base to worship people who are paragon level 100.
This idea was suggested by Kripp, and was widely supported by his youtube followers, so it would make sense for Blizzard to implement because it will either work, or they can say "hey, you guys wanted it, it's your fault." Although the idea had a lot of potential, I don't think Blizzard thought it through very well. Every time I gain a paragon level, I want to unlock something new, not gain an additional dex.