Are you actually experiencing IO bottlenecks etc? A disk queue length of 1.86 doesn't indicate a problem on its own. A disk queue length > 2 (per spindle / indivual physical dislk) would suggest a bottleneck, although occasional spike are to be expected.
So, for example, a 2 disk RAID1 drive showing an Avg Queue Length of > 4 would be an issue, a 5 disk RAID5 showing an Avg Disk Queue Length > 10 would be an issue etc. Also check % Disk Time (>50%), and look for certain *IO* WAITYPES on processes to indicate Disk IO issues.