It may be possible to descend 5000ft in 5 miles, but I wouldn't recommend it on a regular basis, even at just 90 kts in still air it would mean an average of 1500ft/min. A bit uncomfortable........
The complex avionics and systems on the Twin star do need a good bit of reading up for anyone who's not used to a glass cockpit, in the same way that learning to use any piece of electronic wizardry in any a/c is mainly a case of reading the manual combined with trial and error.
IO, you've still got to get a dig in about instructors. I have no idea where you were initially taught, but some FI's do understand a little bit about complex aircraft. Some even fly things like airbus' and Boeings which are slightly more compex than any GA machine no matter how new and shiny.
I do get very tired and exasperated with your constant assertions that instructors are all awful. It is simply untrue, some are better than others and there are some muppets around but the vast majority are very good at what they do. Despite having to deal with the vast ego's of many students and PPL's. (Now I'm generalising, but I reckon I've flown with more PPL's and students than you have FI's to be able to make such an assertion.)