Moving will be made to interrupt spellcasting at a point in time...

[Phe]

Or simple make cast time longer while moving. If a spell has 3 sec casting time standing, then have 4.5 sec if running.

but we have to think of the poor paladin in the PvP situation.
if we can run with the same speed while casting, he will have a horrible disadvantage.
in a year, when PvP actually could be in the game.