Fast geo's can also be used at the right time BEFORE the deposit depletes.
You can also have close to 100% uptime on granite deposits without using refills and probably gold as well using a fast geo.
Other than the fact that they are slow.
I got the idea of buying iron ore instead of mining it myself is because people are selling it. I have tried using ind mines and trying to keep them full but then I was a slave to the game and had to do adventures I didn't want to do just to keep my mines working. Then I tried rebuilding which I have said takes too much time, effort, resources and buffs. Then I thought about buying iron deposits from TO because funnily enough people are selling that too. But its way to expensive. So I buy iron ore and job done.
Its just my way of dealing with iron ore. I'm not saying its the best way or the right way for everyone. But it works very well for me. So IMHO these new geo's are no good for me, but each to their own. The fact that they bring out these new geo's to help with iron ore but for me there is a simple work around making the geo's useless.
Now, if they were to bring out a geo that found twice as many iron deposits at 50% faster mining and an increase of 100% of deposit found all in one and dare I say it, just as fast as a jolly then they'll have my attention. But that's far too good for us.
Once last thing, we have had new explorers which have their own abilities and ALSO they are faster than a tavern explorer. So why are these new geo's not faster than tavern geo's. I think we are being conned lol