I did have a pretty massive issue with the Esc Laf squadron down in Alsace early in the war. Lost an entire flight on a Balloon Busting sortie because they kept flying into the darn mountains.
IMHO this issue has been alteady fixed by one of WOFF UE updates.
AI is programmed to climb to preselected altitude on maximum power. As soon as the preplanned altitude is reached, AI slows down to preplanned speed. There is possible, with help of Mission Editor, to alter preplanned cruise speeds in respect to slowest aircrfat in formation, but I do not know how to limit AI climb to altitude behaviour yet.