Yes! If I am putting it to bed for storage for more than a few weeks, I'll make sure to pull the plug and drain the heater as much as possible. Leaving water stagnant in it can be one contributor to the "sulphur smell" the hot water can sometimes get. If it's been unused for a few months, then I will sanitize everything. The recommended amounts of bleach, for the recommended time, will not cause harm to the heater elements.
Some heater mfg.'s do recommend vinegar to get rid of the sulphur smell. But note, that vinegar is a very weak sanitizer, even at full strength (and I assume you do not have access to the many gallons it would take to have any real sanitization at all on an RV system).
Not including the heater in the sanitization just means you have a several gallon reservoir of possibly "yucky" water to deal with.
Bleach is cheap, very effective, and if used in the recommended amounts and then flushed, is safe.
Even for those that either do not sanitize or use some less effective solution - as long as the source of your water is always clean, the worst you'll get is something growing in it that makes it smell/taste funny. But nothing that will make you ill.
2012 Ford F-150 Eco, Max/Max
Jayco 26.5 RLS, Reese Sidewinder