Hey I write a lot of essays!
I got a 45 in English and I can tell you, I only got a H2B in that nasty politics essay midterm! So I would say you are in good standing to do H2B and above!
Academic writing is very different to writing in English, so I wouldn't be too freaked out. Being a Literature student, I actually had to de-decorate and dumb down A LOT of my language and structure in order to do well. If you don't like the whole airy-fairy I'm showing off my vocab kind of stuff, I would suggest doing a History subject, or a Politics subject, or Sociology/Anthropology/Criminology types.
Literature is really the only subject I have taken where it is even acceptable to use properly advanced sentence structure.
The Arts department likes concise language and structure which is far from flamboyant and straight to the point.
That means that it doesn't matter how you write something, as long as you are alright in what you are writing. Unlike VCE Eng, where the former does matter quite a bit.
Anyway, I personally do not think it is that hard to do well in the essays and it is definitely easy to get top marks. However, I plan to pursue a career in writing and enjoy it very much. With Arts subjects, (as it would be with any Biomed essay), it is really research that ensures you get the marks and not how you write things. Spend your time developing a good argument. And the ASU run really good sessions explaining to you how to do that. They will also go through your essays with you if you need to before you submit them!
Also, I have found that (especially in media comm) the tutors are happy to read through your essays before the submission date and tell you what you need to work on.
I was also concerned about the whole essay thing when starting, as I do like test formats and I am quite sciency in that respect (I did better in Biol than other subjectsss) but I think that Uni essays are a lot less...conceited than VCE essays.
With regards to PBL, I can't take that because I don't do a breadth due to my old gen course. However, I do have three or four friends who took it, and each of them found it quite difficult. Apparently there is a lot to remember with regard to the cases, and there are often technical difficulties to put you off in the tests. One of my friends, who is a straight H2A student (for the most part!) even failed one of the law tests. She got a 97 in VCE, so she's no slacker and she definitely studied.
I have heard mixed reviews about PBL, but most say it is quite hard.