For XP GROUPS Mana isn't an issue for me IF:
1) I have WON instead of focus
2) I have a JB/KEI
3) For the most part I limit my casting to aggro spells only, casting when the terror ticks, clicking veil of marlow when multiples.
With this setup I can occasionally hit other spells, the odd lifetap, vortex of death etc... If I had higher FT I could get away with Focus instead of WON, but with only FT 6 and 5200 mana WON is now a must in xp groups or I am quickly out of mana.
Now I admit I XP with fast pulls and often multiples mobs, so I think I XP to full potential. But if I'm struggling with over 5K mana to the point I have to use WON instead of Focus.. the low end SK's must be struggling as well. I know there is lower end FT gear, but really I'm not going to sacrifice a bunch of AC/HP for a bit of flowing thought. I'm sure once I get another 1K mana and a couple more FT I will no longer have any mana issues.
For Raids, Mana isn't an issue at all.
Anyway, my point, if you have a ton of flowing though and a 6K mana pool you're not going to have any mana issues, especially if using WON. But as a Tier 8ish tank, I have to really limit my casting in order not to run out. Maybe thats working as intended but I suspect that low end SK's must be having more issues, I also suspect that the lower end ones are less likely to post in this forum.. there are some egos here that would make any lower end player to the game who read this forum a little shy about posting.