It's really hard to say how "fine" email is working alone without trying Multi-channel campaigns. We guarantee there are clients out there who don't respond to emails, but who would respond to a LinkedIn message, or other channel. Don't leave leads out in the cold.
It's true that you can run Multi-channel campaigns on your own, but often these become disorganized very fast. The larger your sales team grows, the more difficult it becomes to coordinate multi-channel campaigns. Save yourself the headache with our tasks page, which automatically notifies you of upcoming tasks, and tracks engagement across each channel.
Probably not, a majority of missed opportunities are the simple result of people not seeing your message. Many leads may actually be grateful that you reached them with your extra effort via multiple channels. This shows commitment, and they will value the opportunity to work with you.
It's hard to say which channel is the "best" until you've tried it. The most successful/fruitful channel may vary depending upon your messaging, campaign strategy, or business type. The best way to find out is to run some multi-channel campaigns!