ClassicFCT 
Highly customisable "Floating Combat Text" addon with text anti-overlap behavior similiar to that of WoW Classic.
Use "/cfct" command to open the options interface.
Currently there are 2 configuration presets built-in: "Classic" and "Mists of Pandaria".
Users can create their own presets.
Text display area can be positioned in 3 ways:
- to screen center (with x, y offsets)
- to the target nameplate
- to every individual nameplate (anti-overlap doesnt work in this mode courtesy of Blizzard)
If no nameplate is available (in case the target dies or moves off-screen), text display area can fall back to screen center.
Text can be displayed behind or in front of nameplates and their children.
Animations:
- Fade In, Fade Out
- Directional Scroll
- Pow (a 2 stage scale animation for crits)
Configurable variables include:
- animation timing, scale and duration.
- text font, style, size, custom color or by damage type.
- spell icons for each damage/heal event.
- event filtering, sorting and merging
Explanation of some limitations related to combat text addons: Reddit Link