That would buff Spears or other weapons with long reach since the spear user is normally the guy that keeps backpaddeling away from the enemy while the oppenent tries to get close to him using the sprint function. This would probably only effect Vanguards in a positive way since they are the guys with the long reaching weaponry. However I do kinda lik the idea but would change it a bit. I would say the more swings one makes while sprinting, the less damage each swing deals. For example first hit while sprinting deals 90% dmg, next one 70% etc. That would at least harm this new annoying “hit and run” mechanic introduced with the new sprinting system

Archer: Agreed
MAA: Agreed
Vanguard: Making the kick being able to combo would be an interesting idea, but seems pretty useless since it does nearly no damage. But I agree that the Vanguard does need a slight buff of some sort (preferably something that replaces the sprint attack).
Knight: I don’t think a debuff on sprint would be a good idea. I think Knight are fine. The only type of knight that annoys the hell out of me is the kind that aways sprints around while hitting various people. I think the whole idea of comboing while sprinting is kind of stupid but I guess that’s off-topic.