We should enforce that data-parsoid and html (and later, other render metadata) all shares the same tid before we pass it to parsoid. The element ids used to link metadata with elements can currently change between renders, which means that the metadata is only consistent if it originated with the same render. We currently retrieve the latest render for a revision for each, which means that there is a very small window where a template update could have updated one part of information for the revision, but not the other.
If the tids/etags for both resources don't match, we should probably re-try to retrieve matching versions by adding the tid to the selection criteria. Alternatively, we could encourage clients to pass in the original tid. The advantage of doing that is that we'd also cover templates completely changing the page structure on template update. The disadvantage is client complexity. We could also do both & make passing in the tid optional.