I don't have experience with timing being off a tooth on the Vee but I do have plenty of it on a 450 MX bike.
A single cylinder will be harder to start and run awkward (less a better description) however, it will run. Fairly obvious something's wrong.
A twin with one jug being good, I would imagine it less noticable the other cylinder being off a tooth.
2012 DL1000 Adventure (Tinkerbell)
PC-V, TRE, CR8EIX , ECM, K&N, RDL, PR4, PC-8, EB H4, WERKS, Madstad 22", 17/43 gearing, AdventureTech: Fork brace, shelf, mirror extenders, SpeedoDRD, wheel spacer, Head's-Up voltage monitor, Goldwing pegs, Sonic 1.1. Wolo Bad Boy.