I read that also.
I found another article that stated 1K crit = 3% increase, which seems more probably. My findings seem very similar to you, but with +500 more crit. My crits are very streaky, gone entire battles with arrow strike not criting and have almost every sinlge arrow strike crit. If you want good crits I would venture to guess 5 to 6K crit is a number you strive for.
The highest I have seen on this server checking out the high levels/BRs is around 3K crits, with room for improvement to possibly 3.5 to 4K.