Wyver Druid and some basic questions

I started playing PoE 2 last week, had great fun with mercenary and wanted to try out druid as it is one if my favourite classes in Arpgs. As Bear and Wolf are standard in almost all Arpgs I wanted to go with a wyvern/caster hybrid fire damage build. I started using volcano and tried using rolling magma to explode it. Problem is that the skills itself feel a bit ineffective. Most enemies are so fast they are already gone when the volcano is cast or they just sprint over it without taking much damage ( not too different from mercenarys grenades, but at least there you can reduce the fuse time). Rolling magma is effectively useless once the enemies are in meele range as its cast starts behind them, basically jumping over them. The combo works pretty well with slow or ranged enemies, but I spend most of my time just using the basic wyvern attack. And with how fast and agressive some bosses are I can see it becoming a huge hassle just to get some damage in. Am I missing something? Is Wyvern just another meele option like Wolf and Bear and if I want to cast I go full caster with skills from the elemental tree?

I also started a monk and feel extremely squishy. Is evasion worth it at all? You will never evade everything, especially from big groups. And when you dont have at least some armour I can already see the one hit kills on bosses. With monk I can see going full energy shield, but what about chars like archer? Just spec the tree into armor or shield to complement evasion?

Sorry for the long post, but I just try to wrap my head around a few things, and some design choices just baffle me ( like having massively decreasing resistances from act to act, or the reliance on increasing numbers of aoes and projectile spams on bosses with sometimes arenas getting smaller as the fight goes on), although the game is a lot of fun most of the time.