The order should be Edit then Edit tab. Looks like a hard-coded left somewhere?
Mentioned in SAL (#wikimedia-operations) [2017-09-28T13:38:12Z] <zfilipin@tin> Synchronized php-1.31.0-wmf.1/extensions/VisualEditor/modules/ve-mw/init/targets/ve.init.mw.DesktopArticleTarget.init.js: SWAT: [[gerrit:381210|ve.init.mw.DesktopArticleTarget: Remove hack for reversed tabs in RTL in Vector (T50017)]] (duration: 00m 50s)
After trying to verify the fix during the SWAT deployment, I found out that this entire feature (fixing up the tab order if wgVisualEditorTabPosition was changed and we're seeing cached HTML with the tabs in wrong order) is actually entirely broken and just does nothing. The deployment was essentially a no-op. This is actually convenient because had it worked, it would have been messing up the tabs.