I made a list of the spell mastery abilities (Well, actually I stole a list from an earlier discussion rather than creating it myself). I then divided the list into primarily combat mastery abilities, abilities equally useful either in or out of combat, and mastery abilities used primarily in non-combat situations.
Combat
Imperturbable Casting (p33 HOH:S) may help spells that demand concentration (as when you want to sustain them when you cast another spell).
Obfuscated Casting (p34 HOH:S) is primarily combat in focus
Quick Casting (p34 HOH:S) is almost exclusively combat focused
Rebuttal (129 HOH:S) is primarily combat is focus but it could be used to bolster wizard’s boost style spells out of combat
Apotropaic Mastery (p.122 RoP:TI) is primarily a combat specialization but could be used for wards outside of combat
Fast Casting 87 (p83 ARM5) is a combat specialization no doubt about it
Magic Resistance (p87 ARM5) is for combat but also for avoiding being messed with by subtle mentem spells, wards, and the like
Penetration (p87 ARM5) is for combat
Applicable to either
Precise Casting (p34 HOH:S) would help with craft magic or any other high finesse spell.
Boosted Casting (p99 HoH:TL) is frightfully good (too good in my opinion) for non- combat spells.
Learn From Mistakes(p 100 HoH:TL) would be an excellent tool for removing botch dice
Multiple Casting (p.87 ARM5) In addition to being the most wickedly powerful combat specialization there is, has several non-combat uses. Does a multi cast ritual spell demand vis for every copy? I’d say yes but we’ve debated this before without either side being able to claim their position is the only reasonable interpretation of the text.
Stalwart Casting (p100 HoH:TL) could be handy outside of combat if you’re using summoning spells to control magical spirits and creatures but is primarily combat
Tethered Casting (p100 HoH:TL) this could be used as easily outside of combat as inside of combat
Unraveling (p123 HoH:S) would be used primarily out of combat
Adaptive Casting (p99 HoH:TL) as Yair noted would be useful for an aegis or any other general spell regardless of whether it is combat oriented
Non-Combat
Acute Sense (p71 HoH:TL) is non-combat in focus
Ceremonial Casting (p99 HoH:TL) Can’t even be used in combat
Disguised Casting (p99 HoH:TL ) is about messing with the quaesitors, not defeating your foes
Harnessed Casting (p99-100 HoH:TL ) has primarily non combat applications
Lab Mastery (p100 HoH:TL) is clearly about lab work not combat
Quiet Casting (87 ARM5) you might very well want to be stealthy outside of combat and have very little incentive to be stealthy inside of combat
Still Casting (87 ARM5) you might very well want to be stealthy outside of combat and have very little incentive to be stealthy inside of combat.
I'd say that spell mastery really is a primarily combat focused option but there is a fair amount of support there for making it useful in other ways.