I've almost stopped using the deadringer these days, so much better to use the standard invis watch and just screw with people, spy is however just based on how the other people are doing, even if they have 1 person who keeps screwing you over, avoid them, its not really hard and he can't be everywhere.
and mvm fail? its amazingly fun.
and play on nocrit servers if your annoyed by random crits, problem solved.
also spy isn't all about using your knife, headshot some people if you can't get close, your gun actually is useful!