I like my new Shimano TDR 8'6" MH 2 piecers. Some may like medium action but I have found the meduim to bend too far for liking with a big dipsey out back, but I am good at keeping drag set right. Medium gives a bit more flex at boat for the final battle. 8' is typically a little short for dispey rod, a little easier to land fish by yourself, but reduced lenght = slightly reduced flex for boat battle too. Most dipsey rods are 8'6 or more....
Was just calling around yesterday on this very issue. Craig at Erie Outfitters has the Okuma 8' and 8'6" Classic Pro for around $25. Fished dipsys and inline boards on a friends boat using them and liked their performance.
I prefer a more limber rod than most do. When I hook a small, undesirable, non-target fish, I can take a look at the rod tip and see that he's hooked, rendering a perfectly good setup useless until I unhook him/it.
I have the Shimano TDR's in MH and love them. Never had a problem detecting small fish on the line. Length is personal preference but I run the 8'6 with the dipsy's. They have a good "fast tip" and plenty of backbone.
I like Ugly Sticks for dipseys. They are $30 bucks, come in a variety of lengths and are really durable. I use 7 foot medium action for smaller dipseys and medium heavy for large ones. Graphite/composite rods are not my favorite for trolling because they are too stiff and prone to breaking.