Here is Mumeii's record (NA+EU first Legend tier player)
He has took like 6months 17 days, and played 5 hours avg everyday!
Following is the record exactly when he hit the legend.
6166900pp total
Class Legend
Win Count: 3612
Match Count: 5571
MVP Count: 3932
Winrate: 64.83%
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From and including: Tuesday, September 26, 2017
To, but not including Thursday, April 12, 2018
Result: 198 days
It is 198 days from the start date to the end date, but not including the end date
Or 6 months, 17 days excluding the end date
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Yes, this is simply achievable if you play for a year for anyone just like the way you played Overwatch, CoD, Smite, PUBG, CSGO or other eSports game you have played so far.