The network I'm part of, makes use of TickProfiler, a Forge mod that lists resource-hogging Tile-Entities and Entities, per time/tick average, per tps%¹ they are draining, per chunk² and per type³
¹Take this with a bit of salt. If something states it is causing 50% of the drain, it may very well be a big drain, but the profile cannot see everything, yet tries to stretch what it can see to how much is drained.
²allows you to see the chunks with highest activity, most of the time player-bases centered in a single chunk, for example
³Shows the tile-entities and entities that collectively stand for the most drain. Take this with a bit of salt as well, as it does not take into account -how many- of said type there are.
While this may not solve your issue, it should enable you to find the largest TPS-drains on your server.