My only issue with VAR is when the ref takes too long to make a decision.
You should be able to make a decision quickly. If you have to watch it more than 4-5 times from different angles, then it isn't "clear and obvious" and shouldn't be overturned. Even at the risk of getting it wrong. Let the ref watch a few times from a few different angles, but the whole thing shouldn't take more than 30 seconds, including the jog over to the tele.
or...
Put a timer on the television, once the ref gets there, he/she has 15 seconds to watch the replay, at which point the tele shuts off automatically. If it was clear and obvious, he/she shouldn't have to watch any more clips. If not, it stands.