A significant part of AdWords management involves educated trial and error.
No matter how well you know your product, your markets and Google’s system, there is no way to accurately predict which ads will work and which will fall flat on their faces.
AdWords visitors are probably quite different from your regular visitors – different needs and behavioural patterns, so new strategies may be required.
For all of these reasons, it’s important to try a wide variety of different ad techniques.
I would recommend four ads per ad group as an absolute minimum; but the more different ads you run, the greater the chances of success.
Bonus tip: once you’ve found the ‘right’ ads, don’t make the mistake of then believing that the ad group can be left to run itself. It can’t.