I don't think half the peoples who posted here know the "surecast" buff is lost when you start the next cast, even if you interrupt it yourself by moving, or by beeing stuned/silenced. You just lose it when you start casting something, period.
There is no 10s of free casting without interruption. You're thinking about the pvp skill (which should remain as it is).

If you're THAT worried about it breaking the class in pve or pvp, just reduce the potency of the spell affected by 33% or 50%, in a similar fashion as swiftcast is now in pvp. It will remain inferior to swiftcast anyway, changing this cooldown to over 1min would make no sense.