I had a similar issue in 6.3 with long tooltip descriptions being clipped off or not fully displayed in a dialog. I solved it by putting 2 new styles in a new CSS clientlib assigned to the coralui2 and coralui3 categories. These styles allow the long tooltips to wrap to multiple lines.
/* Style to correct tooltip alignment when the tooltip is left of the icon */
left: auto !important;
right: 25px !important;
/* Style to correct tooltip alignment when the tooltip is above the icon */