Is it just me or Does Combined SE flair takes more time to update than Individual Sites Flair?
I have noticed that all my Individual sites flair are up-to-date almost all the time; but whenever I see my Combined Flair, it's not updated!
Yes, combined flair is slower to update than per site flair. This is explicitly stated on your flair page:
at the bottom it says,
No, that's probably by design.
Per-site flair is provided by the site itself. For example, my Physics.SE flair has a URL
On the other hand, my combined flair is
All SE sites cache inter-site data. For example, your rep and badges here and on the accounts section here will be slightly outdated, that's by design. Since
On the other hand, the per-site flair need not use cached data, and even if it does, it can afford to update the cache much more frequently than the cross-site update.