My current employer has an avamar grid and has been doing the vmdk backups... All db's in simple mode and no "real" sql backups occur. Some of the larger systems have backup exec installed still but we have to get off of it. So we're working through how it would work to do avamar sql plugin or if we need something else. I have litespeed licenses for the largest db's but we'd really like to have all the backups in one spot if we can.

I'm going to do some testing of the avamar sql plugin because the vmdk backup strategy leaves you in a "crash consistent" state. Transactions in flight could roll forward or backwards when the logs replay, and if for some reason there was some sort of corruption introduced at the point of snapshot, it could be failrly unpredictable is my take on it.

The real question to ask to answer whether you need an agent or to make native backups or compressed backups or whatever you are thinking of is this:

What are my RPO, RTO and SLA on the system in question? Can the product I'm evaluating meet these requirements? Do some testing to make sure. Maybe you make a compromise and you backup the largest ones with a redgate or litespeed and then back those files up with avamar or whatever other backup system you are using. Maybe you use full avamar sql backups (if you have the network bandwidth and grid size to handle all your stuff). Maybe you use native sql and back those files up.

The answer is fully dependant on your environment's configuration, but I've found with a little testing and knowledge of the RPO/RTO/SLA objectives you'll find success.