Although https://hub.spigotmc.org/jira/browse/SPIGOT-1626 is marked as fixed, chunk loading is still very terrible in the latest version. Looks like md_5 knows what was going on, this still might be a vanilla issue but I'm not sure. Better to keep this issue known though i guess ;]

From timings, these stick out the most:
syncChunkLoad
chunkLoad - Post

and shows up in minecraft total:
ChunkIOTick

Last update was a few hours ago and I'm experiencing it too. (4 behind)
Version posted below.