Atleast now we know there is a tanglable reason for putting points into cetain elements. Wish they would be more clear on what part the Guardian plays.
Thats what open Beta is for. I created characters with different guardians/classes and leveld them on the same mobs to the same level to see how the guardian influences them. I did the same for elemental affinities (yes, it's affinity not resistance).
Needles to say it is not quite as simple as putting 100 points into Fire affinity and suddenly Fire Crystals start raining from the sky. That would be so not SE. There is however a significant influence on almost everything in the game with these affinities and guardians. The guardian affinities are however less pronounced as you can not change them as easily as your elemental affinities. They are still significant enough to be nnoticable right away.
Everyone can test this really easy in OB within 2-3 hours. Might as well use the time constructively since everything get's wiped in a few days anyways.
Got any numbers or scenarios as examples? :)
First thing i did was at start of Open Beta when i got annoyed getting killed by the Funguars outside of Gridania due to them poisoning me. Beeing a FF11 player i concluded Poison is a water based spell so let's crank up my Water affiinity to the max. 2 Respecs later i was sporting +60 Water Affinity and i resisted some poison attempts. But the most noticable difference was that the poison effect was already wearing off after i got hit with it. I took about 2-3 "ticks" of poison damage then it was gone. Before that it would last for 10 or more "ticks".
It did not change the damage the poison did however. If it was a 30HP/tick poison effect it stayed at the same damage, just shorter.
Another easy and good way to test this is to strip naked, get the alchemist crafting tools and start making Distilled water. You want some physical level so do all the Rank 1 guildleves at the starter camp first (takes 30min max).
The recipe is simple and perfect for this test. Muddy Water costs 76 Gil and uses one fire shard to make distilled water. Make sure you have no affinity in Fire and do 2-4 stacks. Use only Standard synthesis, no wait and note the Durability/Quality if you succed, number of failed synths and if you want to get fancy number of failed/succeded standard synth actions.
Do the same but now put all your points towards Fire affinity.
I did the same with the guardians, start a new character and level on one type of mob exclusively on a low pop server. You'll be surprised what you can find.
PS: There is a form of treasure hunter in the game, you just need to know how to activate it. Every one can have it. I won't share it yet as it needs a bigger sample size but it's effect quite noticable and affects more than just mob/crystal drops!