We don't know what truly happened on Baltigo right now, as the only info we have are from the perspective of the World Government, plus given speculation on how strong Dragon is and general scaling from Sabo, Blackbeard could've easily been fatigued at that point. Teach doesn't seem like the type to partake in unnecessary battles either.
Alternatively, CP0 could simply be a top tier force. Whilst not canon right now, Hybrid Lucci was capable of fighting Sabo for a short while in film Gold, making him at least Burgess tier until proven otherwise. In the Heart of Gold special, a random CP0 member was also capable of equalling someone on par with Gear 2nd Luffy, so if the group is large enough, they could prove troublesome to the Blackbeard Pirates after facing all the Revolutionaries.