At the moment we have a lot of experience boost from the anniversary event. For the time being you probably want to turn off the extra experience using the /purist command. /purist also forces you to use classic drop style, but since you're soloing it won't affect you.
I'm not sure if this will be sufficient to stop gaining xp too quickly. If it does, there's not much choice except to make another character to experience the other episodes.
Another problem may be getting weapon drops that would trivialize early areas in other episodes. In this case, try to do one area at a time, and somewhat cycle through the episodes. For example: Forest->Temple->Caves->Spaceship->Crater(all, any, your choice)->Mines->CCA->Ruins/Seabed/Desert->Tower. This is just an example. Different areas have different quality in weapon drops, there's actually a sequence you could follow which would stop you from getting later weapons too early -- but I didn't actually check if the example I gave follow it well enough or not.