Elemental is in a bad state for PvP and fixing our mana regen is just a small step, but this should help.
Current rolling thunder: has a 60% chance to proc off lightning bolt and chain lightning, restoring 2% mana and adding a lightning shield charge.
Proposed change: Your lightning bolt and chain lightning have a 60% chance to gain a charge of lightning shield. Each time your lightning shield does damage, you gain 2% mana per charge.
Everything stays the same for PvE, except you get mana in bursts rather than gradually. Whenever you use ES with excess lightning charges you gain that mana back (7 charges = 8% mana, 8 charges = 10% mana, etc..). Net mana change is nothing, assuming your not leaving your lightning shield stacks at 9, which you shouldn't be doing anyways.
For PvP, every time you take damage you get mana back. Instead of having to cast LB or CL to get mana regen, you get it through taking damage or unleashing your excess Lightning shield charges (if people aren't tunneling you allowing you to stack them up, which is almost never). The glyph would remain the same (can go below 3 charges from taking damage), but it would still give you 2% mana for every time it proced (assuming it's staying at 3 charges).
The only down side to this is if you anked or were b-resed, it would take you a little longer to get mana back.
Comments and thoughts welcome.