The Oryx designer works well currently on Firefox and Chrome.
We do aim to support IE wherever possible, but it is not always easy, especially around more advanced features like the web designer canvas which isn't well supported on IE. We will aim to update Oryx for IE compatibility at some point. In the mean time can you please point us at your alternatives that you are considering that provide executable BPMN2 from a 100% web based (non-flash) solution that work in IE? That would help us better understand the various options.
The issue btw. seems to be the way IE handles JavaScript and has not to do with html version support.
Thanks.