Aren't the Sazh/Vanille sections generally thought of as...notably harder than Lightning/Hope?
No. With the proper application of buffs and debuffs no. People for the most part from my experiences at the FFXIII boards find these sections difficult because they think they can just wade in there RAV/RAV and COM/RAV style like they've been doing with Lightning and Hope. Which of course doesn't work because Sazh is slow (casting/attack speed) and has crummy stats. They aren't used to properly integrating buffs/debuffs into the system yet. Once the proper advice is given to them regarding buff/debuffs and they apply it the Vanille/Sazh - Sazh/Vanille sections suddenly become a lot easier. When the SAB/SYN roles are properly utilised together with an offensive drive and worked into decks with other roles those sections become an absolute breeze (and not only that properly integrating them into the rest of the game knocks the stuffing out of it too ;p) Saboteur is an offensive role in the main for the most part not a defensive one. It slows the chain gauge and prevents decay like COM does stabilizing it and preventing chain level from dropping which enables Vanille to act like a pseudo COM in her sections. In addition to this as dude pointed out she is significantly boosting over all future damage output by applying debuffs at the same time. With Deprotect, Deshell and Imperil all out she is certainly more than tripling offence for when your characters switch into their main damage decks. During my FFXIII replays where I knew how to fully apply my knowledge and experience from my first whole run through the game (including post games) I integrated better paradigm decks for the Vanille and Sazh chapters from the get go which did indeed make them become an absolute breeze, a walk in the park as Adray would say
Undermine (SAB/RAV) is a much better starting deck for those two than COM/RAV. I had Vanille doing thousands of elemental damage as Ravager too (RAV/RAV) once I switched her to it after significantly weakening enemies with debuffs and stabilising chains with SAB. She is better than the real deal with her pseudo COM Sabness during those stages of the game (Sazh gets trolled yes - well ok Faith on Vanille helped with finetuning the damage output)
Because that's essentially what you are getting from her early.
Well to be honest I am fine with this because truthfully I now have tons of early game Vanille/Sazh respect. They are top choice for ally priority for picking to go with Lightning at the end of Chapter 9. Early Imperil, Haste, Deprotect, Brave, Deshell, Faith, Poison and En elemental spells are all great stuffs. Haste and Imperil are especially incredible/amazing, they are two of the best abilities in the whole game
Vanille can also do multiple status effects at the same time once she gets going. Deprotect/Deshell are 53.3% chance of inflicting the status per use, Imperil has a 39.9% hit rate per use. This is without factoring in Improved Debuffing factors for the Belladona Wand series. Vanille will definitely eventually be applying more than one status a round. By the time she picks up Imperil and with the Belladonna Wand three at a time isn't impossible.
*Deprotect - physical damage taken increases by 89%
*Deshell - magical damage taken increases by 89%
(Tal says it's actually a bit more than this in practice too~)
*Improved Debuffing - Increases the status hit rates of Debuffing type abilities used by this character by 1.2 - 1.2 the normal rate
*Improved Debuffing II - Increases the status hit rates of Debuffing type abilites used by this character by 1.4 - 1.4 the normal rate
(credits go to the FFXIII Game Mechanics guide and Tal~)
Vanille also gets MT Deprotect, Deshell and Imperil - Deprotectga, Deshellga and Imperilga.
Maybe if Raise was really early, but don't think it was.
Not really early but relatively so I think? Raise is Stage 6 Crystarium for Vanille (which is the stage unlocked after the Havoc Skytank boss at the end of Chapter 7) She picks up all the more potent/higher tier MED abilities like Esuna, Cura, Raise and Curaja earlier than Hope at least. For example Hope doesn't gain access to Raise until after the first boss in Chapter 10 (Stage 8 Crystarium)
40% MT with Curaja which goes to ~55% in the aftergame)
Curaja also gets more potent/powerful the less HP targets have too. It can restore as little as 1% (1HP!1!1!) when max HP is full becoming much more potent when characters are badly wounded