I use a combination of inline CSS to control line-height:
<p style="padding:0px;margin:0px;margin-auto:0px;mso-line-height-rule: exactly;line-height:110%;font-size:11pt;">paragraph text</p>
The key element is the Microsoft proprietary CSS attribute, mso-line-height-rule: exactly;. The padding just prevents the paragraph tags from creating unnecessary space.