I would think it was a bit lame if someone named their kid Johanna but pronounced it Joanna, honestly. That said, I actually like all three pronunciations:
yo-HAHN-ah
jo-ANN-ah
jo-HANN-ah
Three boys nappin', one mama namenerdin'
To peruse my top 100ish names:
http://www.behindthename.com/pnl/82589
He is becoming greater, I am becoming less
Bits of the journey here:
http://jodifriesen.blogspot.ca/And some family cuteness here:
https://www.flickr.com/photos/41705228@N08/