10 minutes on a single site? It is extremely “odd”.
It supposed to be a few seconds. It depends on your hosts/servers/networks/sites of course, but most of the time I can’t tell the difference in speed if I upload/install/update directly on the client’s site or thrum MainWP even from our European server to our Aussie server location.
Actually, with MainWP you can drop and install/upgrade several different plugins (security, SEO, backup, etc.) at once on multiple sites (don’t need to add them one by one).
It’s a bit hard to give reasonable advice without more details on your setup.
Ps.: I’m currently managing 20+ sites with MainWP without any problem (and slowly converting some of our Joomla sites to WP). MainWP is fantastic and the main reason we’re switching to WP.
All the best,
Joseph Simony
Selfmed.pro