Tobacco is generally a pretty strong flavor, and depending on the flavor, and vendor, the percentage will change. I have a bottle of "Cowboy" blend tobacco juice from Ecigexpress, and 1 drop in a 10ml bottle throws it off balance, so yeah...it really just depends. Perhaps people with more input and testing will chime in; but my suggestion is avoid the flavor tha ti made the mistake of getting. I thought "Hey, I'm a cowboy, I live in Texas, and grew up smoking Doral full flavors, then went up to Marlboro Menthol, then Salem Black Labels, then Newports, then Marlboro Reds, I can take this...NOPE...it's disgusting.
I've honestly found that a lot of the vendors I bought pre-mixed tobacco flavors from too weren't that great. A few of them got it, but Tobacco flavor just REALLY wasn't my gig once I started
vaping.
I've found I lean more towards fruity, and "light" flavors; even my menthol lacks the "tobacco" side of itself, and tastes SO much better!
If you haven't already, I say go without tobacco flavoring, and try for things you typically wouldn't like, for me, it was strawberry, and watermelon. They're DISGUSTING flavors to me to vape, but once I popped a few drops of menthol in them, it was a WHOLE NEW BALL GAME! They were awesome!
Good Luck, and Vape On!