I think that after the defending team loses an objective, it should go into a "neutral" state before another team can cap it. Once it becomes neutral, then another team can start capping the point. However, another team cannot start capping until they return the point to neutral. In order to capture a point, they would an attacking team would need to kill the lord, get the objective to neutral, and then fill it with their color. To make up for having to through the neutral state, points should be easier to cap. Should a point be partially capped but no (valid) players be inside the ring, the capture point progress won't decay. For the purposes of world score, an objective will still be held until another team fully captures the objective.
As an idea for a new tactic, how about a downstate lord? One where when the lord is killed, he goes into a downstate and has to be stomped before the point can be capped. When he is first downed, he is also broken, meaning stunned and 50% increased damage for a few seconds to allow for cleaves. This will be for keeps and smc only, and can only be used once. Meaning after a keep's lord has been downed, he won't he can't be downed again as long as that that team holds the objective; after that, the lord will simply die when he is killed.