"It is always useful to talk about these things" is a perfectly correct translation. The word order is not the problem. There are many such problems in Duolingo, but it is still a wonderful tool, and why complain about a free gift?
I cannot understand why they used the singular form "è" . For me the right answer should be: "Parlare di queste cose sono sempre utile" since "queste cose" is plural (These things). Can you help me with this guys?
Would you say "Talking about several things are ..."? No, because the subject of the verb is '"talking". Similarly with "Parlare". Even if you translate it as "To talk about many things is/are ...": you'd say "is", wouldn't you?