Let's face it, RMM tools weren't built to be backup checking technologies. They were built to Remote, Monitor and Manage computers, servers and the like.

Reliability

Most of the RMM tools utilize SNMP or PowerShell to check backup jobs through application logs which can be quite buggy at times. We've seen many examples where the RMM tool reported a success yet the backup wasn't running for weeks. SNMP and PowerShell will likely never be a reliable method for checking backups because it depends heavily on the server or computer working properly. Add to that the potential for an RMM agent to be unstable (I know it never happens right?) and you could be spending vast amounts of time on the phone with your RMM vendor trying to fix it. Configuration and upkeep on an RMM tool for this purpose will take up a lot of tech hours. 

Trending 

Most RMM tools can give you the quick and dirty of whether a server has a successful or failed backup in most cases. What it doesn’t give you is a great trending dashboard for all of your backup products. It usually provides no real view into how often your backups are failing and if the same backups failing. If backups are in different places then the ability to see trending is a problem.As a result there will be gaps in backup processes and checking.

Custom Thresholds and Tagging

RMM tools will only tell you if the last backup was successful or not. For backup administration custom thresholds are critical. This allows you a way to prioritize your backup checking processes to ensure that your backup admin handles the most critical servers first. If you can't tag those servers as mission critical and prioritize your remediation time then you could be putting your client at risk for data loss. Your backup admins only have so much time in a day and you need it to be spend making sure your most critical data and systems are protected. 

Schedule Based Tracking

What if you have a backup that is scheduled to run only during certain time periods? RMM Tools will report that as a failure until the time period and will take no accounting of the date and time period with which you expect a successful backup. These failures will likely also show up on your reports meaning that you will have to explain them during an audit or manually fix the report. 

Multiple Servers In a Single Backup Job

Many backup providers allow you to backup multiple servers with one backup job. In this case if any server fails it will report a failure for the entire job. This means no way of separating the devices into metrics per device that make sense. An RMM tool will see the entire job as a failure and your backup report will reflect the single job as a failure. 

Reporting With Multiple Backup Products In Use

Simply put RMM tools do not do a great job of reporting on disparate backup systems. Though it can usually be tweaked to check results, it will almost always fail you when it comes time to gather data and report on this data on multiple products.