Living in Brussels currently. Tbh I would think very carefully about it. As you say the tax rate is high, and on top of that you will have to get health insurance. Health insurance covers most of but not all of the cost of appointments and procedures so you are normally left with a smallish bill at the end on top. Of course having said that the health care system in Belgium is generally more efficient than the NHS, as you would expect.
 However as a Brit I really resent having to pay such high taxes and then more on top for healthcare haha. 

I find Brussels in general quite a 'Marmite' city - some people love it, some really hate it. I have to say that in the winter it is bleak - cold and very overcast for about half the year. The area you live in is very important - make sure you do your research about the different 'communes'. I would strongly recommend that you visit the city properly - spend some time walking around, getting to know the different areas and ask yourself if you can really imagine living there. Cost of living is not as bad as London, but it's not exactly cheap either. 

Socially it's a good place - huge expat bubble, although a lot of them work in the EU institutions, so can be a bit hard to break into the social groups if you don't. People will tell you that you can get by in Brussels without speaking French and while that is *technically* true, you should either already be confident, or make a serious effort to learn. Not speaking French (or Dutch, in Flanders) makes it extremely difficult to integrate and makes dealing with the authorities much harder. Also personally I think it's just a matter of respect for the locals, it drives me nuts when people won't even learn conversational French/ Dutch, depending on where they live. You will also find it hard to find a job (even in tech) if you don't speak at least one of the national languages decently.