Unfortunately you wrong. Upgrading troops, spells, and heroes does not reward any experience points. Thus your statistic is focused entirely on defensive progression and does not incorporate offensive progression.
Of course, with this last update, it is incredibly easy to see where someone is on their offensive progression just by clicking their profile. I forgot about that fact when I replied. So in any case, you can just compute your statistic and then glance at their profile before making your decision. In all, I'd say useful.
On an off-topic, I would love it if Supercell would give us more profile statistics to better screen potential clanmates. For example, average attacks/war, stars/war, etc...





