If the tools you are using are working to your satisfaction, then I see no real reason to switch. I wouldn’t say that they are all the “best” solution for each particular task however.
There is nothing wrong with decrypting with DVDFab HD Decrypter, unless you are working with a very new blu ray or dvd that has just come out and has a new protection scheme on it. In those few instances, that program usually lags behind on updates (deliberately by DVDFab) and just won’t work on them for a few weeks.
Handbrake uses the X264 encoder, and is very popular. It should work fine for small mkv or mp4 files using the X264 encoder.
DVDShrink is a good transcoder, but if you want the very best quality when compressing a dvd video to fit a DVD5, you should use an encoder like HCenc. DVDRebuilder can use HCenc, and will give slightly better results. The free version of DVDRebuilder is now pretty old and may never be updated, but should still work for this. The Pro (paid) version has more options, but if you have already ripped just the main movie using DVDFab HD Decrypter, that won’t matter much.
You haven’t mentioned what program you use for compressing Blu ray, and keeping it in blu ray format. I suggest BD Rebuilder for this. You can make AVCHD compatible movies to fit blank dvds, or you can compress blu ray to fit 25gb blank blu ray disks. It can also convert blu ray to dvd-video or make H264 .mkv files for you. It also has presets for your iPad.
Imgburn is very good…no need to change this.