When to make changes to the cost threshold for parallelism
Using MAXDOP = 1 can be a help, but it is a big gun.  It may be that the actual problem is the usefulness of the indexes.  Perhaps a new or a different index would resolve the problem.

Following Mr Denny and Aaron Bertrand's comments, did you discover what other waits in that connection were likely the cause of the CXPACKET waits?  

Jonathan Kehayias suggested a query that might help you assess you parallelism experience and make a more thoughtful decision.  But you should also read the conversation between Jonathan and Paul White.

https://www.sqlskills.com/blogs/jonathan/tuning-cost-threshold-for-parallelism-from-the-plan-cache/