I just completed the "Rise of all Goblins" campaign by defeating Splig. I was shown the aftermath screen with "The "End" in the bottom right corner. After that an ad started playing for a new expansion/campaign. When I click the ad to end it I'm returned to the main screen. I can the choose to load a game, but when I do I'm brought back to the beginning of the final encounter with Splig. I then re-ran through it by just clicking through the encounter and defeating Splig but the same thing happened. Am I not able to use the two heroes that I was playing, their XP, and gear, and start them on the next Campaign?

No, you do not carry characters over from one campaign to another.

Then is what I stated common; that after completing the final encounter of a campaign you're brought back to the main screen, and if you load that save it just brings you back to the beginning of that last encounter? This makes it seem like you didn't complete the campaign.

I can't remember exactly what displays at the end of the campaign, but going back to the menu, win or lose, is normal. The save file being before the last encounter is because of how the autosave works. There's no spot where it saves after the campaign ends, and not much point to having one anyways.

I think this indeed an oversight or a bug. Usually the save file should be deleted automatically once you complete a campaign.

Thanks so much for the help then. I was really confused on how we should move on to the next campaign. This leads to another question then. I know that Rise of Goblins is the tutorial, but are the other campaigns longer? Is there enough content in them to get into Act II gear?

The other campaigns are indeed much longer than the tutorial. In the tutorial you can play between 1 and 2 story quests as well as up to 2 sidequests in total.

"Kindred Fire" or "Seeds of Corruption" allow you to play 6 story quests and up to 10 additional sidequests, so there is plenty of room for acquiring and using act II gear

Much appreciated folks!