I don't think you would see any decrease in the polling rate. The issue is that you are WAY over extended on this polling engine and you require a secondary poller at this time. The max number of elements per polling engine should not exceed 12k elements and you have 20,259. The number of interfaces you're polling seems to be the biggest impact. Unless you intend to get a secondary poller, the next step should be to reconsider which interfaces you're polling. Typically you only needcritical interfaces such as WAN, uplink, internet links etc. By default when you run a discovery or add a node, SolarWinds will pull in every active interface and in most situations it isn't necessary to have them all. You can probably search right now at least for Null0's and delete those interfaces at minimum. I'm an Engineer with Loop1 and we provide professional/consultative SolarWinds services. Feel free to DM me or reach out to me via email at the link below if you have further questions (no cost).
Loop1 Systems: SolarWinds Training and Professional Services