I think the drop rate isn't terrible tbh, I will admit a lot of xs do drop, it does take a while to save them up and it does seem unachievable for many
I think the key issue here is one of people setting realistic goals for themselves. Everyone seems to have a mindset of 'best or nothing'. If you add a DC+8 instead of a DC+10 everyone will laugh and say you've ruined it. Oh no, you're down 2 DC, how will you ever survive /s
E runes are an option for the biggest spenders and 24/7 players. Casual players can't realistically expect to have exactly the same standard of kit as people who spend thousands and/or live in the game. But you can get remarkably close
Let's say you have boots you want to socket with DC, that's 4 socket spaces
To add all (E) will give you +60 DC and will require 972 XS runes
To add all (XL) will give you +40 DC and will require 324 XS runes
To add all (L) will give you +32 DC and will require 108 XS runes
To add all (M) will give you +24 DC and will require 36 XS runes
If you're a casual player, consider using M or L or even XL at a push on your kit. Think objectively at exactly how much DC you're going to miss out on. Look at it this way, if you have four L runes in store and could put them on boots but would rather wait and save up to use your XL, what you're really doing is paying around 600gg extra (or grinding to find an additional 216 xs runes, which could take months for a casual player) to gain a whopping 8 DC in total
If casual players accepted that and used smaller runes, I think we would see an uplift in general satisfaction
The only reason I'm spending stupidly on SC runes on tao is to try to be the highest SC on the server, a silly competition I've got into my head, and gritt seems to be the only competition at the moment. For normal purposes it's simply not worthwhile. I like that there's an extra tier available for people who want to spend wastefully and go a bit nuts. Even on my wiz and war I still use XL, I don't see any problem with it. On lower characters I have I've got no problem using L runes of stuff like celestial kit etc. Other people need to realise that and rune their kit to an appropriate level rather than expecting to be able to +15 everything without spending a fortune