Yeah, I have been having the same problem mate. I'm just using all the relevant terms out of the suggestions. I never really take the volumes into too much consideration. If it's relevant, it's relevant, so use it.
Animated, I can definitely confirm that for non-English languages at the moment (at least German and Italian). Traffic Estimator gives no or almost no data for non-English keywords. The English data works fine.
This is definitely not the usual statistical uncertainties but completely missing data chunks for whole languages.