No, generally not. When it is time to do a particular poll, the messages are queued up.
What you are seeing is normal.
Leased groups are not as helpful as you might think if the leasing situation has parts of tags in both paces. Optimization is based on top level tags (controller tags and program tags). If leasing targets a specific top-level tag in more than one pace, you can actually increase the message load.
Have you seen this topic (and the ones linked within) ?