This is base mana regen.
This doesn't include the ability to gain mana back from, for instance, VQ+Widow Makers, where attack speed does matter.
You can get mana regen on the main hand weapon, zuni mojo, and a non-zuni helmet. This would give maximum possible mana regen (and still not enough :\)
The class is designed to use a lot more mana than other classes, so in the end, you need to offset that by getting +mana from items (which is actually kind of hard), mana tactics (we have several to choose from!) or mana runes.
Take me for example, I don't have the greatest gear but I took two mana tactics already for WoS spamming. I need either Swarm's devouring rune for farming or Haunt's draining spirit for uber fight or else I can't sustain the spamming even with only 1.53 attack speed. I could have used Searing Swarm/Acid Cloud for more aoe damage but that pushes my mana cost quite high.
Yes! I can change my Tal Rasha helmet but that means I'll lose out on Critical and there is no way I can afford a Critical Zuni helmet. I bought my Mojo specifically because it has +14% SB and +mana regen. There were mojos with higher Average damage/INT but I know I need +mana regen and I paid for it. (For the record, I did not buy Tal Rashal, those two were drops for me)
The point I tried to make is that we have options but it seems like we need to go out of way to get them when other classes can mostly just focus on the typical Attack Speed, CC/CD. We could have taken more runes with more damage potential but if you don't have enough +mana, you need to take runes with +mana rune which sacrifices some damage.
However, unlike most here, I care more about how we can get more damage that don't cost mana and I don't want Mana on Critical because that is just too similar to Wizard/Barb. Yes, I am looking at Fetish, Thorn and skills that are still under-performing.
Seriously, how good is WD without Zombie Bear? How many of you are going to use Zombie "Charger"?