Blocked queues are (obviously) bad for your environment so here a search to identify those:

index=_internal sourcetype=splunkd group=queue (name=parsingQueue OR name=indexqueue OR name=tcpin_queue OR name=aggqueue) 
| eval is_blocked=if(blocked=="true",1,0), host_queue=host." - ".name
| stats sparkline sum(is_blocked) as blocked,count by host_queue
| eval blocked_ratio=round(blocked/count*100,2)
| sort 20 -blocked_ratio
| eval requires_attention=case(blocked_ratio>50.0,"fix highly recommended!",blocked_ratio>40.0,"you better check..",blocked_ratio>20.0,"usually no need to worry but keep an eye on it",1=1,"not unusual")

Example result: