Okay, exp log. At the start of this I'm 3855/4700 (partway into Level 8 ). For perspective, I also have ~1300/15000 gold for the next story mission and have cleared catacombs level 5. I've also bought all the outfits (but only two weapons because I don't like the stats on the others).
All exp values are for an individual sister.
Noble Robbery #1 (threat level 5-

: 194 xp, -100 gold (old man), bunch of gems (forgot to count) and 2 medium healing pots
49 - Food Cart: Heavy Guard, Watch Dog x2, Veteran Guard
27 - Random: Watch Dog x2, Veteran Guard
48 - Random/Trap: Heavy Guard, Light Guard, Watch Dog, Medium Guard
70 - Coffin Trap: Four giant spiders
Noble Robbery #2: 432 xp, 166 gold, 200 gp gem
39 - Guarded Door: Light Guard x3, Medium Guard
35 - Trapped Floor: Light Guard, Medium Guard, Watch Dog x2
74 - Random: Elite Guard x3, Retired Mage, Watch Dog
72 - Plant Trap: Giant Plant, Corrosive Plant x2
158 - Pit Trap: Giant Snake x3, Acid Snake
54 - Thief Ambush: Thief x2, Assassin x2
Noble Robbery #3: 107 xp, 152 gold, 3350gp in gems
52 - Plant Trap: Giant Plant, Carnivorous Plant
55 - Guarded Vault: Medium Guard x2, Light Guard x3
Noble Robbery #4: 292 xp, 2100gp in gems
25 - Cellar Entrance: Giant Bat x3, Vampire Bat x2
24 - Random Encounter: Watch Dog x2, Veteran Guard
74 - Trapped Floor: Light Guard, Medium Guard, Heavy Guard x2, Watch Dog (This tipped me to level 9)
88 - Trap! Earth Elemental Boss
81 - Guarded Vault: Light Guard, Medium Guard, Heavy Guard x2, Watch Dog
Ended at 4880 exp, so roughly a thousand above where I started and 5285 gold (I haven't sold all my gems yet).
So on average, it looks like I need 17 encounters to go a full level, or 85 between story missions. If the last mission suggests level 25, that's 425 battles (for reference, I think someone was saying SotW was a bit over 400 if you did everything). On the other hand, four robberies got me over a third of the way to the 15k story mission if I sell everything. Thus, approximately a dozen robberies plus a catacombs level and I'll have the gold, but only 3/5 levels.
The boss fights feel like they could give a tad more exp, they offer about the same as a normal encounter, and even though it's just a single mob and roughly the same difficulty, the exp boost would make them feel more like a bonus so they stand out. Also I'd say boost the guard amounts, they seem undervalued (slight boost to Light, more to Medium, Heavy, Veteran because of their abilities). And the bats also reward very little for how powerful they are - I actually got too cocky and had to retry this fight.
The tutorial said that mercenaries houses offer more exp, but I need ever increasing amounts of gold for the story and supposedly they don't offer good rewards. (I haven't tried one yet.)
Back to typos:
Moirgane.rpy 1900:
The tavern return
ed to normal...
Moirgane.rpy 1917:
as much as she would
have liked... (to match the tense of the rest)
rooms.rpy 956:
Still, can't sell it on. We should rob whoever makes them. (She's talking about a chair, but I think you're missing a word in the first sentence.)
MaryAnn.rpy 552:
...the next day (no s)