First of all, thanks for your kind words!
Many people would expect that an English teacher's job to push his or her students to increase their vocabulary, practice new grammatical structures, and express every more complex ideas in English. So they are right to reward students who use new vocabulary and who take risks in class.
However, I don't think doing the IELTS writing test is the same as writing in classroom. It's not the time to take risks.
It's time to show that you are competent and solid, not the time to take flights of imagination or to dazzle the examiner with a brilliant display of linguistic virtuosity.
If you are writing a piece for a college newspaper or magazine, that's different. Let yourself go. Knock yourself out. Dazzle and amaze all you want. Set no limits on the flow of your argument and the range of your eloquence.
But not in IELTS.
I'd say the best thing to do in the IELTS exam is to keep things simple, write 250-350 words in the 40 minutes, and not get too stressed.
Try and have either three very good, fully developed ideas on one side of a topic, or about six shorter ideas if you are giving both sides. Have a short clear intro with an opinion and a thesis sentence which says what you are going to do. Have a short conclusion which summarizes nicely and looks to the future. In between, have simple ideas and a mix of short and long sentences. Try to keep your average sentence length below 15 words.
It's a game with particular rules, a style that's different from writing a poem or an editorial in a newspaper or the wording for an advertisement. Keep it simple, stick with what you know works, and you'll be fine.