I have play only for a week so far and am still trying to find out what I want to play through the entire game and all its difficulties.
Like my title say, I like to know if there is a downside to start in Crucible and get the first 5-10 devotion points?
No. It’s a great way to start IMO. Do waves 1-10 a dozen times or so. EZ levels, EZ loot, EZ devotions.
The only downside is that you will start over-leveled and will have a boring time until you reach Burrwitch where the experience starts getting decent again. Besides that, nah, there aren’t any downsides.
Although it trivializes Act 1 up to the Warden, it’s worth it in my opinion for the levels, equipment, and money, but most important is the easy to get 10 Devotion points meaning you can cap your Devotions by the end of Elite if you don’t do the expansion as well (mid-Elite if you do the Expansion).
it will trivialize the veteran and elite playthrough. 5-10 more devotion points is huge. much bigger impact than being a few levels ahead of the curve