Plenty of email marketers/providers have discussed this pain point, but the key idea is that Outlook uses Microsoft Word to render HTML emails, and Microsoft Word was not optimized for that purpose.
There is never a one-size-fits-all solution because Outlook performs in unique, and odd, ways with different WYSIWIG editors.
What can I do if I want my emails to work perfectly in every platform, and near perfectly in Outlook?
The best suggestion we can currently advise is to switch over to complete HTML designs, and work with a provider, such as Litmus, to ensure that HTML designs perform flawlessly in every platform. (Even then, different versions of Outlook render differently, so it may not be perfect.)
What are the repercussions of not doing customized HTML for my Outlook users?
Very low or almost non existent for most our partners, as you can see by taking a look at stats over here. Outlook's share of the email market is typically not a large enough concern to warrant cost intensive design solutions.
In the long term, if Outlook changes their rendering approach, then their inbox may start automatically working with most WYSIWIG editors.