AD/HP Rengar build actually works fine than we could expect?

I saw a guy builded rengar like that few days ago,

and he carried single handly. His damage was insane, his survability was also good, he didnt have any resistance but he was relied on rengar's W i guess?

then I saw a rengar in a challanger streaming today, the only difference in his build was having Dominiks regards instead s.gage.

is this build really works? Cant wait to try. Should I max W second or E? and the build order should be leaving tiamat untill late-game or rushing draktharr in case you have normal kda.