Notice the kneeling pose Tifa is in during Part V, after coming out of the flashback. It is the exact same pose she has in FFVII when in critical status - in other words, right before unleashing her Limit.
Equipping Materia gives you powers, but decreases your total HP. Tifa may have lost her magic when she lost her umpteen bazillion materia, but given how many lethal-looking attacks she tanks after...
Rewatch DF I and II again and notice the tactics used. While the FF girls tend towards teamwork and combination attacks (like the Haste casting), the DOA girls try to force one on one battles, and only gain an upper hand when the FF girls are outnumbered (and therefore splitting focus). Since DF III on has the girls separated, the DOA girls are showing their superiority. Now comes the real Fridge Brilliance: Think about exactly what kind of games these characters come from. While the fighting game characters are more effective in one on one battles, the RPG characters are more powerful as a team.
Possibly leading to even more brilliance when you consider just when the Final Fantasy girls start to kick ass. In the first video, Team FF start getting their act together when Tifa joins Yuna and Rikku and brings their total number to three - the smallest possible "full" party of any Final Fantasy game. The team gets to an almost game-breaking level of power when Rinoa and Kairi appear, bringing their number to five - the largest party possible in any main-numbered Final Fantasy game.
In Dead Fantasy V, when Tifa is hallucinating before her Heroic Spirit moment, it shows her waking up at the tower from Dead Fantasy 1, in the same place she jumped in and saved Yuna and Rikku. A single white feather falls down by her side. Given that Rinoa has the ability to teleport people and that she has white feathers on her wings, could it be that she was the one who transported Tifa there to help Yuna and Rikku in their hour of need?
A female warrior appears over a battlefield and whisks the heroines in battle away to do battle elsewhere, in more brutal and savage conditions, apparently in preparation for a greater battle. She comes complete with sword, shield, and wings, completing the classical look associated with a certain Norse god's agents. That's right; Rinoa is a freaking Valkyrie! Of course, Fridge Horror might kick in when you remember that the Valkyries were the "Choosers of the Slain"....
Dead Fantasy music videos. They say if one should want to maintain their appetite for sausages, they must be careful as to not being present when they are being prepared. The music videos, too, apply: the gentleman responsible for these impressive animations are said to have employed the technique of mocap-ing himself in order to capture the delicate, acclaimed movements. The subtle hip movements near the beginning of "Obsessed" may lose their savour once a viewer learns of this truth.