Most delays in a switching environment are due to traffic issues. This may not necessarily be an obvious issue such as regular unicast traffic but more often that not, an issue in regards to multicast, broadcast and flooded traffic. Assure that this is not an issue. If all of your switchports are in one vlan, a good test may be to move two devices into a seperate vlan and run the pings again. If they are stable, then you know the issue is with traffic on the original vlan. Check you show controllers ethernet-controller for the ports in the original vlan and view the TX multicast and broadcasts to assure they are not incrementing rapidly
