Closest thing to pre-legion damage text possible with the current API limitations. +icons, colors, filtering and more.
Description
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
MIDNIGHT: This addon cannot be updated to work as intended on the post 12.0 version of the game. The game client simply doesn't provide enough information during combat to reimplement even the most basic of features that this addon is expected to have.
Pre-Midnight Explanation of some limitations related to combat text addons: Reddit Link