Furthermore I think DNC has less Crit Hit/DMG gear and gifts than THF (excluding random augs), meaning that Tauret could probably be a bit further behind than it is for THF? I dunno...
I wanted to unpack this part a little. Right now, I just limited my search to the Evisceration sets listed in THF and DNC guides, since I'm assuming that people have done math for total Evisceration damage and take into account other factors like the WSC contribution to base damage or otherwise choosing to use a different piece over something with higher crit chance/crit damage. I haven't examined this too closely, so I just wanted to provide that disclaimer.
Guides I was looking at for reference:
THF:
https://www.bg-wiki.com/bg/Community_Thief_Guide
DNC: obviously this very thread
https://www.ffxiah.com/forum/topic/53853/the-last-dance-iii-a-dancers-guide-new/#_user-5-ws
Some things to keep in mind about crit chance: common to either job, there's dDEX (max 15%), "Other" category merits to increase crit chance (5% at 5/5), and Evisceration has an inherent 10% crit chance at 1000 TP, scaling up to 25% at 2000 TP, and 50% at 3000 TP. Not sure if the crit inherent to Evisceration is just for the first hit or for all hits, though.
As far as traits/gifts inherent to each job, they both get 8% total Crit Damage in job point gifts once mastered, and in traits, THF gets 14% crit damage (tier IV) while DNC gets 11% (tier III). So, before gear, THF has 22% crit damage, DNC has 19%.
Gear-wise, the capped attack THF Evisceration set gets +35% crit rate, not accounting for mainhand or offhand. I can't find anything in THF's abilities that increases crit rate, other than Trick Attack and Sneak attack forcing crits -- I'm not as familiar with THF, so it's possible I'm missing something.
Pieces in the THF set I was looking at that have +critrate: Yetshila +1, Plunderer's Vest +3, Mummu Wrists +2, Moonshade Earring (+250 TP translates to +3% critrate from 1000-1750 TP), Mummu Ring, Begrudging Ring, Toutatis's Cape augmented with 10% crit rate
Gear-wise, the DNC Evisceration set gets +24% critrate (or at least the Dream Tier set, which eschews the critrate+ rings in favor of Regal Ring and Ilabrat Ring -- but it doesn't list variations for attack (un)capped situations).
Pieces in the DNC set I was looking at that have +critrate: Mummu Wrists +2, Lustratio Subligar +1 Path B, Odr Earring, Mummu Ring, Begrudging Ring, Senuna's Mantle augmented with 10% crit rate
In addition, DNC can use Building Flourish to add 20% crit rate to all hits of their weaponskills. In my experience, the cooldown is still high enough at 10s that I TP fast enough so that each Evisceration at 1000 TP can't be boosted by Building Flourish -- I'd call it every other one?
DNC can also add +14% another critrate by debuffing the target with Feather Step Lv. 10, if it's not too impractical for the situation. THF can benefit from this too if another DNC in the party/alliance does this, but if a DNC intends to Evisceration spam with Tauret, they can guarantee they get a boost to crit rate with Feather Step this way.
As far as crit damage goes, the attack capped set for THF has +22% crit damage.
Pieces in THF set that have +crit damage: Yetshila +1, Adhemar Bonnet +1, Plunderer's Vest +3, and Pillager's Culottes +3
(THF does have a few more +crit damage gear available to it, like the AF +3 hands and crit damage augmented Herculean Boots, but I'm not precisely sure why they're unused in the set. At a guess, Mummu Wrists +2 for critrate, and Lustratio Leggings path D for STR for attack and fSTR and DEX for dDEX and WSC.)
Dancer's Evisceration set has +26% crit damage.
Pieces in DNC set that have +crit damage: Charis Feather, Adhemar Bonnet +1, Meghanada Cuirie +2, Herculean Boots (assuming +4% crit damage augments), Senuna's Mantle (on base stats of cape; crit damage isn't an augment path)
Obviously, Maculele Tiara is an option for +25% crit damage if we're using Climactic Flourish, but that only applies to the first swing of a weaponskill.
Offhands like Shijo for THF (provides both critrate and damage) or Skinflayer augmented for crit rate or crit damage (mutually exclusive augments) can add more, though Twashtar seems like the best option if available (I assume to cap dDEX and contribute to the WSC component of Evisceration's base damage).
So, in summary, ignoring offhand options:
THF gets 35% crit rate and 22% crit damage from gear, alongside the max of +30% more crit rate at 1000 TP assuming capped dDEX, merits, and the 1000 TP crit bonus inherent to Evisceration and 22% crit damage from traits, totalling up to 65% crit rate and 44% crit damage.
DNC gets 24% crit rate and 26% crit damage from gear, can debuff the enemy for 14% more crit rate, and can use Building Flourish for at least 20% more crit rate from the job point category alone, alongside the same assumptions for THF about merits, dDEX, and Evisceration's TP contribution to crit rate and DNC's inherent 19% crit damage from traits+gifts, that totals up to 54% base crit rate before Feather Step or Building Flourish (68% with Feather Step Lv. 10, at least 74% with Building Flourish, and at least 88% with both) and 45% crit damage.
I'm not discounting that there might be some other disparity between THF and DNC Evisceration that exists (like I've completely ignored multiattack procs and Thief's Triple Attack damage, fSTR, total DEX for WSC), but unless I'm missing something major (like I just looked at those specific sets, which might be a form of cherrypicking), I don't
think it's in anything to do with crit rate or crit damage.