From a lore perspective, player perspective or just for fun?
By the time you first reach Lord Dorian's castle, Mila should be around HR 25-30, less if you've been avoiding everything or never talking to Faahlda (poor Faahlda - though technically, it allows players to completely bypass leveling after HR 16 except from rank up events).
Consider the following (a good bunch of which are mentioned in MKRU's guide):
- Mila can buff her ATK from multiple sources. ATK from states and ATK from buffs stack.
- Dagger, Daggera and Daggerga will inflict SW, SW2 and SW3, which
also stack. The Dagger (lowest tier) skill shouldn't be used though because both forms are immune to SW (but not SW2 and SW3).
- He has a 200% Light weakness. You have many ways to use Light, including physical attacks by using Light-infusing gear.
- Blood Goad, like all regular RMMV buffs, is capped at two buff levels, meaning Dorian cannot get more than +50% to ATK and MATK from this. No, he cannot pull off the hilarious stuff the legendary magma enemies could do if they cast a Fire spell on themselves in Breath of Fire 3 (or if you did, because that's an insane source of experience if you do manage to beat them massively buffed beyond the cap), he'll still have to live with a measly 285 ATK
fully buffed (up from 190).
- His second form may be intimidating (due to the increased stats) and annoying (Blood Moon Carnage and Disruptive Wave) but it also has a 270% Light weakness, and again, it can be afflicted with SW2 and SW3. If you're coming here before you met your Guardia, it isn't a problem either, Mila doesn't even need buffs or summons to make short work of the weakened state.
Short answer, drinking blood all the time would only have accelerated his downfall since he's literally wasting turns. The second form is huge - which means it has huge guts - but in the end it's also very weak and if you destroy it before it even manages to finish casting Blood Moon Carnage or even cast it at all (quite possible with multihits), it'll go down in confusion and madness.
The above is not possible with False Memory I because it is quite tough, resists all three levels of Silver Weakness, hits hard and is VERY fast; twice as fast as Dorian's last form extra turn wise, before even accounting for AGI. Its only real weakness, Light, also only is 130% damage. You still have access to
the Guardia, Dawn Bringer, the Double Band and the Revenge Plate at this point and Mila will be nearly unstoppable as long as it doesn't get to cast Disruptive Wave too often. If Mila already is a powerhouse as she is (that's a lot of laurels even with ultimate gear), she has zero needs for buffs since she cannot go over the base stat cap in combat (which means Disruptive Wave just causes it to waste a turn instead of you wasting turns rebuffing).
(If I had to pick my favorite battle though, the Alexandria Omega one was the most reminiscent of Final Fantasy, Chrono Trigger, Breath of Fire, Persona, etc. hidden or last bosses strategy-wise, and the 1 HP skill then unexpected entrance that can drive an emotional player to tears is a very nice touch. False Memories are quite powerful but unless you don't remember how you fought them they're just stronger versions.)
I believe there's another weirdness though MKRU. If you willingly lose to Alexandria's first form (or just get rekt somehow; she's not exactly much of a threat if the player wasn't mean to Bianca) and then refuse her deal (love Faahlda's face when Mila goes NEVER) she'll proceed as intended but... then
move on to her next form with scared Mila and Faahlda still onscreen as the Omega parts are building up for the final battle. All of this happening at the same time looks REALLY weird lol.
Also had a glitch happen when going through a Chaos Door with the canceller (the one that leads to the Forsaken Cathedral when you're backtracking) that left the inverted colors onscreen even after exiting the Chaos area. Leads to hilarious psychedelic battles and Mila's comments are even funnier than usual in this mode (they're the regular ones, but I don't know, it just makes her funnier lines even more amusing).
Next testing step, play every single scene of the ToI and see if there's one that breaks something.