Should steroids be avoided? Good question. If you have normal blood pressure I would say on balance, yes. If you don't and can barely stand up but have the muscle strength and energy levels to, but are disabled by OI, you could consider it perhaps.
There have been reports over the years of the medication Florinef (Fludrocortisone) making some people with ME CFS worse though. This would at first seem contradictory as cortisol is often reported to be reduced in CFS research studies. One can conclude/presume from this that for some reason when you have ME CFS the body needs cortisol to be lower. Potentially this could be that ME CFS patients have a hormone sensitive infection that replicates in the presence of steroids including androgens, thus making patients worse, over time. Certainly If we think of the age of onset of ME CFS sufferers and who is affected most severely, then adolescents and young adults seem to be especially affected by severe grade CFS. These are a group of people with very high hormone levels compared to people in their 50's, who in the majority, are often less severely affected. Maybe food for thought there when considering the option of starting corticosteroid or indeed taking testosterone if you're male or HRT if you're female.
A better drug for ME CFS if you have severe OI disabilities, in my view, and want to boost your orthostatic function is Midodrine (Gutron). This is often used for POTS or for those with low blood pressure on standing, such as syncope disorders, and OI found in conditions with CNS damage. The benefits of Midodrine is it isn't a corticosteroid, however, it does have some unpleasant side effects.
Getting a prescription to this medication is not routine. Unfortunately, Midodrine requires the permission of a specialist to order it. Take it in a safe environment to see if you can tolerate it (It constricts blood vessels and may cause chest pain and very high BP). You also cannot take the medication and lay down flat afterwards (risk of supine hypertension), so not very useful for those who are bed ridden which is ironic as its the only drug I can think of to literally be able to make people who cannot sit or stand upright, do just that.