Using red anchors on sliders that match the vocals (like 00:01:192 (3) or 00:04:942 (4) ) is a good way of representing rhythms without increasing the difficulty.
(Although the vocal sounds are slightly earlier than the red anchors would imply, being 1/3 after the slider's head - for example, the red anchor on the slider at 00:04:942 (4) should hit the slider ball at 00:05:098 rather than 00:05:166 to match vocals entirely.)