cross class skills for DoM class/jobs

[-DMR-]

Are there useful cross class skills that can be used with DoM classes/jobs? I have quite a few empty slots here and there, at the moment.
I'm currently aiming towards getting Stoneskin spell (more useful than Protect spell?).

[Niwashi]

The most important one is probably Swiftcast from Thaumaturge (level 26).

Stoneskin and Protect are both useful as well. (Though if there's a CNJ/WHM in your group, it's better to let them cast Protect, since when you cross-class it you don't get the Proshell trait that makes it stronger.)

[Anova]

It depends mostly on your role. Swiftcast is universally useful for all casters, although healers place a particular premium on it for Raise and dps purposes. Black Mages get it automatically, while summoners can speed up their rotation by applying a dot or placing a shadow flare in the initial pull.

DPS casters really want to level archer for Raging Strikes (lv.4) and Quelling Strikes (lv.34). These will increase critical hit rate and reduce enmity, especially useful for black mages who decide to double- or triple-flare in the first 20 seconds of a fight, or summoners who want to crit all their aoes and bane/fester without pulling from the tank in the iniital pull.

[ruskie]

Raging strikes is a damage buff not a crit rate increase.

[Anova]

Raging strikes is a damage buff not a crit rate increase.

I think I remember that patch they changed it from crit to damage. Guess it never registered. Thanks for the update.

[Garlyle]

Conjurers borrow from Arcanist and Thaumaturge and really, really want Swiftcast (THM 26) above all else. Surecast is occasionally nice to pop to ensure your casting of Cure III/Medica II won't be interrupted during a boss' big unavoidable attack, but Swiftcast is beautiful - it's about the only way you'll reasonably be able to cast Raise sometimes (it removes the 8(!) second cast time) and even without it is just amazing for emergencies. Getting Virus and Eye for an Eye from Arcanist are also helpful, but far from essentially - still, there isn't really any other competition when you're a WHM.

Thaumaturges pull from Arcanist and Archer. Eye for an Eye, Virus, and Physick are nice to have, but the low-level Raging Strikes from Archer is invaluable for what you want to be doing - and later on Quelling Strikes is near mandatory to go 'full ham' without pulling the aggro of everything in the room because nobody can output damage at the start of a fight the way a high level BLM can.

Arcanists borrow from Thaumaturge regardless, and they want Swiftcast first and foremost - not just for Ressurects which can be cast regardless of Summoner/Scholar but also for when their pet dies (The loss of your pet can be 30-40% damage/healing lost until you've got it up and running again, and cutting out 8 seconds of standing there can make all the difference in the world). You should also consider grabbing the Conjurer's Aero spell while you're still an Arcanist, as it gives you another DoT effect.
Summoners will also borrow Archer skills - much like Thaumaturge the key is Raging Strikes, although popping Quelling Strikes if you have it at the start of fights can help out some too (It's rare summoners have problems with accidentally taking aggro though).
Scholars will be borrowing Conjurer skillls. Namely Protect and Stoneskin. As mentioned, these spells are more effective if an actual WHM casts them due to traits, but inevitably you won't always be partied with a WHM so having them on hand yourself is invaluable. Scholars can also uniquely borrow Cleric Stance, which will enable them to swap into mildly effective DPS as necessary.

Prior to obtaining your job at 30 (Jobs restrict your cross-class options to only two other classes in exchange for a number of benefits), you also have a few other skills you can consider. The majority are actually useless to casters, but you might consider the following that haven't been mentioned: Internal Release (Pugilist 12) increases your Critical rate for its duration, and if you've been up there, Blood For Blood (Lancer 34!) increases your damage output at the cost of some defense, although I'd only grab that if you had it anyway instead of levelling for it specifically. Foresight (Marauder 2) and Featherfoot (Pugilist 4) are defensive cooldowns that will help you when soloing or if your tank sucks at keeping aggro off you, while Bloodbath (Marauder 8) and Second Wind (Pugilist 8) are cooldowns that will help restore some of your own HP.

[-DMR-]

Ok, I'll see what I can sort out.

Anyway, once I'm done acquiring the Stoneskin spell with WHM (and putting it with other classes), I'll focus on DoW classes and get them leveled up to 30, so I can have a choice of dungeons as well as more abilities/traits.

[Vorpal_Spork]

Are there useful cross class skills that can be used with DoM classes/jobs? I have quite a few empty slots here and there, at the moment.
I'm currently aiming towards getting Stoneskin spell (more useful than Protect spell?).

Look up the job on the wiki and it'll say what cross class skills you can use. http://ffxiv.consolegameswiki.com/wiki/Jobs