I'm juuust about in range of a bunch of contracts in the 20s to mid 20s and you still get XP from those (several hundred each), so I might be able to hit 20. Mid 18 now.
The bug only seems to affect certain quest lines in the main quest, all in Novigrad (Broken Flowers specifically). I'm close to done with Velen and Novigrad anyway, so I'll just keep going. Hopefully the main quests in Skellige give XP again. I've been wearing Witcher gear and XP trophies 95% of the time, which might even out my losses.
I'm still impressed by how fleshed out the side content is. You can tell where they hide the lack of bespoke animations for certain things, but otherwise their quality is up to par with the main quests. It's seriously impressive. This is the equivalent to W2s two versions of Act 2.