The lack of topic sentences defeats the entire purpose of having paragraphs. The proper length for a paragraph varies, depending on the content and the importance of the information. The topic sentence is supported by a few, well-chosen, additional sentences. If your paragraph runs on and on, your readers may glance at the first sentence or two, then skip to the next paragraph. Never bury the key points in the middle or end of a long paragraph.
Short paragraphs make emphatic statements.
Use them sparingly. The continuity between paragraphs is as important as the internal structure of the paragraphs. Sudden changes of subject will make readers stumble, but choosing a suitable ordering for your topics will often let you flow smoothly from one to the next. When no ordering seems to work, try breaking the text into separate sections, each on a separate subject. Within a section, paragraph breaks can be made less abrupt by anticipating the next subject at the end of one paragraph, or by referring to the previous subject in the topic sentence of the new paragraph.