Yes the Mirror Image/Decoy or dodge burst is still fine but those skills have twice the cooldown of the berserker and don't cripple your target. It most certainly does effect pvp. Factor in the dodging/blind preventing casts these add up to big changes. Honestly shatter builds pre the last 2 nerfs were more faceroll than backstab thieves ever could be with less counters.
Still doesnt affect the burst. It only affects damage done before or after the burst. The burst uses a stun/immobolize so cripple isnt needed and when bursting even with the delay the clones should still hit while the opponent is stunned /immobolized they arent attacking during the burst. This unintentional nerf/bug really only affects the fighting outside the combo burst.
As with any burst all you have to do is block it and its probably the most obvious burst atm.