Sounds normal. This is an issue with the on/off style thermostats like the one that you got. Higher end proportional thermostats don't have this issue.
While not prefered the temperature flux you described will not be an issue.
Do you think I should use a secondary heat source to help with the temp flux? The only issue I have had so far with using one (e.g. light bulb) is it seems to suck the humidity out of my tank.