70%Critrate/300%Critdmg/1950+ attack

I've been playing for 2 months but based on my experience, these kind of stats, or something slightly lower, seems impossible to get. Getting 2 crits in a single unit is already difficult, let alone getting high rolls for them. Clearly, it's not impossible since I'm seeing a lot of players that has kind these kinds of stats in a lot of their characters but how.

Is there any optimal strategy on upgrading and tuning echoes?