I looked at Mysterion's screen shots of a Warden with full defensive self-buffs and a Guardian with Guardian's Ward up. That's the best data I have. For the sake of this evaluation of partials etc. I made the assumptions that we're dealing with common damage and that there is an additive effect between Partial <something> Reduction % and Common Mitigation %.

Warden:

Common Mitigation: 49.9%

Block: 25.0%, PB: 10.0%, PBR: 55.0%

Evade: 20.0%, PE: 7.7%, PER: 55.0%

Parry: 19.8%, PP: 7.6%, PPR: 75.0%

All partials get absorbed.

In 90.1% of all attacks the Warden takes no damage. The remaining attacks get mitigated which means that he can expect to take a total of5.0% of all incoming damage.

Guardian:

Common Mitigation: 66.8%

Block: 25.0%, PB: 12.8%, PBR: 62.5%

Evade: 5.1%, PE: 2.2%, PER: 47.1%

Parry: 17.8%, PP: 9.0%, PPR: 75.0%

All partials get absorbed.

In 71.9% of all attacks the Guardian takes no damage. The remaining attacks get mitigated which means that he can expect to take a total of9.3% of all incoming damage.

So your conclusion seems to hold up based on these numbers, Wardens do in fact take less damage than Guardianson average, though they are of course still susceptible to spike damage.

I don't know how Partials get affected by Finesse but if they don't - at all - we can play with the idea of simply reducing the avoidances as one lump as all partials are absorbed by both classes. Thus using the "popular" 9% Finesse we get:

Wardens:

In 81.1% of all attacks the Warden takes no damage. The remaining attacks get mitigated which means that he can expect to take a total of9.5% of all incoming damage. That'sup by 4.5%(or a 90% increase which is a silly number to use in this context as absolute numbers make more sense).

Guardians:

In 62.9% of all attacks the Guardian takes no damage. The remaining attacks get mitigated which means that he can expect to take a total of12.3% of all incoming damage. That'sup by 3.0%(or a 32% relative increase).

My conclusion:

Yes, the Warden does get hurt more defensively than the Guardian by Finesse. However, if the data samples are representative, the assumptions hold, and my calculations are correct, the Warden is still in a very nice place in RoI. It could be argued that the difference is made up by the Warden's greater susceptibility to spike damage.

It would require about 25% Finesse to make Guardians and Wardens take equal amounts of expected damage at which point they will take about 17.5% damage (and the Guardians will haveserioustrouble getting block and parry responses).