Generally a passive system mechanic, damage and defense modifiers are something to be wary of as the round comes closer to an end. It's one thing to be aware of the possible damage output based on the current resource situation, however one step past that is to start considering modifiers and how they will affect said damage. Here are the factors to be aware of that affect damage and defense values.
Having equal health or the health deficit will guarantee that your damage output is 100%. Normally this is not something you should even have to consider, however in DFCI when you have the health advantage your damage output is actually lowered by 10%. There is a HUD element towards the end of your health bar that turns white when you have the health deficit. This is useful for many reasons, the most important being that you can easily tell when your damage output is increased or decreased, as well as knowing when Reflection Guard costs no meter.
Since potentials are usually activated early or midway through a match it is usually not something to consider when going for the winning combo, however it is something to consider when sitting on full meter and deciding when to spend it to maximize damage. Not every character’s potential gives damage or defense modifiers so each character that does will be listed below.
Attack Level 1 (10% damage increase)
Asuna, Shana, Mikoto, Shizuo, Tomoka, Taiga, Rentaro, Akira, Emi
Status Up Level 2 (12% damage and defense increase)
Tatsuya
One of the more important activation elements of damage modifiers is the universal potential. When your health is at 30% or lower your health bar turns purple to signify you have entered the universal potential (upon exiting the potential your health will return to yellow), followed by a 10% damage increase. This comes into play towards the end of the match because if you have the resources the additional 10% damage increase can decide whether or not your combo will defeat the opponent. Universal potential applies to every round, however going into the second round after losing the first your damage is increased to 20% making it an extremely important asset when factoring in how much damage you can deal to the opponent.
Specific to Ilya, Ryuuji, and Holo, these assists can also grant damage and defense modifiers to the player. All three assists give Status Up Level 1 after activating their requirements, however when Iriya finishes her third bowl from 5S, the player is granted Status Up Level 3.
+15% damage, last 10 seconds
+5% (Red TC) , +10% (Blue TC)
+3%, 7% damage per boost
Rather than treating damage and defense modifiers affect two separate entities, I feel it is easier to simply think of it as what your current damage output is. View the opponent’s defense modifiers not as a modifier that increases his defense, but instead a modifier that decreases your own damage output.
It is possible to have multiple Status Effects concurrently active, however in the case of damage buffs only the highest buff will take priority (i.e. Asuna's Character Potential which gives a 10% damage buff stacked with the 10% damage buff from the Universal Potential will result in only a 10% damage increase and not 20%. However in that same situation with Tatsuya, his 12% damage and defense buff from his Character Potential will take priority over the smaller 10% Universal Potential buff. In addition if Power Blast was used, then the 15% damage increase from it will take priority over the 12% damage buff but will not erase the defense buff). Defense buffs do stack, for example KYH with Double Player Ignition (10% defense buff), Mode Green Trump (15% defense buff), and Status Up Lv. 3 (18% defense buff) from Iriya totals up to a defense buff of 43%!