I was thinking of just doing the vault on easy difficulty, but was wondering if I should save my keys until I can handle the harder difficulties. Are the rewards worth it to wait?
As the tool tip says you get more loot, in the way of keys and resources but not in troops and orbs.
Normal is 100%. 10 gem keys
Challangin is 110%. 11 gem keys
And hard is 120%. 12 gem keys
You are betting off using them. More often than now you get troops. 4 vault keys in a row gave me cedric its ridiculous and only going to get worse each passing campaign
It would be best to use your VKs on hard difficulty once you have the necessary troops, weapons and stats to safely win there. But if you really need the extra resources now, then just do the highest difficulty you can handle.
To help determine how high of a difficulty you can handle, use the explore difficulties below as a measuring stick. If you can consistently beat the given explore level, then you can safely do that difficulty of vault battle.
Normal: Explore 3
Challenging: Explore 5
Hard: Explore 9
Do you need orbs, because you’re a new player? If so: use the keys.
If you wait too long, the resources are getting more and more meaningless, even if you get more.
Using them to power up yourself quicker is way more worth.
The only real reason at the moment I see to save them (outside of being able to do the high level ones as mentioned) is if you are waiting for a tarot card from a campaign to be released into the vault. However, if you partake in the frequent vault weekends there is likely less of a need as you can replenish your keys.