It is not doable in tableau.
I don't know the exact reason why you want to show labels at an angled view (which is typical excel view). From the data visualization best practices, you want to keep labels to horizontal so the user does not have to tilt their heads to read the labels. Currently in Tableau, labels are shown vertical or horizontal and not an an angle. I don't know if this answers your question, but we'd loved to to share some best practices. As for the label truncation, Tableau is doing its best to present the information to you and sometime it suppresses alternative labels or sometimes truncates to fit in the space given. I'd suggest either increase the space for labels to fit or change font size.
..hope this helps.
In Tableau, we have only two ways (horizontal & vertical) of Axis label layout possible.
Hope it helps.