Offhand can have block but no other pieces can get block rolled onto them using Obsidian crystal. If you want block on say a ring, a hammer, a chestplate, you have to find a legend that has it. It isn't limited to warrior class despite the old claim that you needed to Jasper offhand to warrior for Block when in fact you don't really. I think you could potentially get block on a pet affix roll too but I am not sure.
As for dodge, it's very flexible and can be added on all gear . Even dexterity 20 gives an extra 10% dodge and you have 10% base dodge do you already get 20% dodge before you add crystal affix. With crystal affix, you can have 50% dodge which is helpful.
On some builds, both helps. On other builds, you either have one of the other. Warrior does benefit from block mainly because of the bulwark talent which can add 10% block for 5 seconds and keep adding but warrior with high dodge also helps or both.
Rogue benefits from power stat 99 which already gives almost 30% dodge on its own which is a huge head start along with the dexterity affix but I haven't seen them having 10% base dodge. You also need 50% dodge on rogue for stealth as well to function at 100% dodge aka dodge everything. Every class can use the 50% dodge 100% dodging stealth but rogue can extend the hero points of stealth easier without relying on pet or 5+ All Skills.
You can't really go wrong with either dodge or block or even both . It just depends on if you have the crystal affixes for it and other slots. It's vastly better than adding HP and damage reduction though since you can't have 100% damage Reduction even in PvE and reduce enemy damage to 0 and it takes too many slots for HP and damage Reduction.
Back when bloodmagic and MP absorb was OP which was many many years ago, it was easy to have huge HP and leech made it so you could be untouchable as well as MP Absorb but those days are long gone so dodge and block are the main uses for high floor climbing.