Since I couldn't find a description of how much the Rare Vanguard Rune of Binding affected healing skills, I did some experiments on my minstrel. Although the tooltip says it adds 76.8 to Tactical Healing Rating, how do I know what the base number is? Whatever the base number is, how are the actual healing amounts calculated from that? As I discovered with the Rune of Striking on my hunter's bow, different skills can be affected by different amounts.
These tests were done traited blue in resonance with whatever traits and legacies I have. Your numbers may be different, but the overall effect is clear.
Adding the +76.8 Rune of Binding to my songbook increased most skills by 37%. Soliloquy of Spirit 26%, Fellowship's Heart only 3%.
The heal over time part of Chord of Salvation was not increased, similar to bleed DoT not being affected by the rune of striking on my hunter's bow. Soliloquy of Spirit (which is only a HoT) was increased but by a smaller amount.
One question was whether adding one to my sword would do anything, since a sword has a tactical damage rating, not a tactical healing rating. In fact it did.
Adding a second rune of binding to my sword further increased most skills by 27%. Soliloquy of Spirit 20%, Fellowship's Heart only 3%. The two runes provided a total increase of almost 75% for most skills.
These results suggest that the base Tactical Healing Rating is half your level. At level 115, that's 57.5. Adding the 149 for a maxed songbook makes it 206.5. 76.8 is 37% of that. Adding one rune raises it to 283.3. The second rune's 76.8 is 27% of that. Adding that yields a final rating of 360.1.
If this hypothesis is correct, then the Incomparable +96 rune should increase healing skills by 46%, and a second +96 adding another 32% giving a net gain of 93%.
The bottom line is that adding a rune of binding to a songbook significantly increases healing, and adding a second one to the weapon significantly increases it further.