I haven't heard of a university/college that had professors who refused to see students during office hours - that's ridiculous.
Now the clincher is that if you'll actually get your question answered when you meet with the prof. It seems profs can be notorious for roundabout answers and speaking volumes while answering nothing. You can usually get a good feel for how they'll be 1on1 when they respond to questions in the class. If they're succint and directly answer the question, go for it. If they refuse to say "I don't know" and go on tirades in circles then avoid them.
Our medchem prof was the worst prof I've ever seen, of well over 70+ professors, for answering questions.
Actual Conversation:
"What does this sulfur group do at position 10?"
"Well, yes. Here's one thing: the molecule was discovered by serendipity which is amazing. It was used in the '50s with great results but patients began to develop [insert disorder here]. A lot of money went into this compound to try and better the class in general through research."
"No, at position 10, why is there a sulfur there?"
"Well this is one thing. The metabolite is the active compound, a prodrug if you will. It was noticed that in dog intestine there was only 26% absorption which showed significantly reduced bioavailability for the oral form. Here is a drawing of the metabolite [draws something completely different on the board, no idea what the hell it is]. This drug is not available in Canada [WHAT THE HELL, WHY ARE WE STUDYING IT] but is available in Africa [AWESOME.]."
Then you get the test and one compound has a sulfur there and one didn't, and it'd say why is A better than B.
We had this guy for a full year, it was absolute torture. He was outdated, wrong on MANY accounts and completely oblivious. Great times. My friends and I actually joked that if we failed med chem we'd have to drop out, there'd be no way to handle him for two years in a row. It wasn't really joking.
