Hello Diana!
I totally agree with the points you listed, ESPECIALLY Phrasal Verbs and Slang!
After teaching in a number of countries for almost as many years the two biggest problems I'VE encountered is ...
A) A lack of confidence
B) (especially if they are adults) Using their native language grammar when speaking English (e.g. "I can English speak." instead of "I can speak English.")
"A" is easily remedied by just getting the student to speak more and to more people (i.e. take them out to a coffee shop and have them order in English). "B" requires a bit more work on the students part. Best thing YOU can is giving the student much Tense work and exercises.
I found this page while doing a Google search and thought it might help a bit more...
Do students with limited spoken English have to push themselves? - TOPICS Online Magazine for Learners of English
I know you were hoping for a students opinion but I hope this helps!
Best!
Melissa