For a send off or penalty try, I would prefer the refs to be 100% certain.
But the Sin Bin in terms of 5 or 10 minutes is way under used at present and should be used for:-
1) Dissent.
2) Dangerous or foul play - tripping, lifting tackles, bad head high tackles, etc.
3) Professional fouls including preventing scoring a possible try.
4) Repeat infringements defending the try line.
5) Diving or faking injury (after a warning)
We will get a better standard of officiating when players respect the refs.
Coaches are instructing players to push the boundaries in ways which are not in the spirit of the game, that will always happen unless the refs have the authority to prevent it.
As I see 5-10 minutes in the bin should not change the outcome of the game.
I would like to see 5 minutes used for offences at the minor end of the scale, with that player being able to come back on after the opposition scores a try.
In particular a player should have to do something bad and blatant to be sent off, I don't want coaches querying a send of in their press conference.