If you merge the decks, it's easy to export a subset using tags in order to look at statistics if you need them.
As to the purpose of stats, everyone has their reasons. For myself, some are more useful than others.
I think the Kanji stats are over-rated simply because you don't know the context of each Kanji being counted. If you use a RTK deck, you're getting 100% stats which is know is meaningless. Plus, we don't know what on-yomi and kun-yomi are getting covered, which holds higher value when you begin reading native material and come across new combination of Kanji vocabulary. Still, it's nice to see more and more kanji get crossed off as time goes on.
Granted, my main purpose for stats is to see how much I've done over the last xx months. It's nice to see I did 50 hours of studying and 6000 items reviewed in 30 days. If I slack, it's right there in my face. Plus, that little function was added recently.