So I've got a question regarding a hybrid Fire/Light Sorc. Should I max one mastery or split it evenly between both masteries? What is the current prevailing thought of the community. Specific build is Thunderstorm/Fire Ball.
It sounds like you're building with Thunderstorm as secondary/backup damage for fire immunes. Since Fireball is your primary spammable, I'd advise that you focus points on Fire damage first.
Typically max your main damage dealer as that is what you'll be using 90% of the time. For any points left over that you don't need for your main skill, can go into your backup. That and gear up your merc. Combined should be able to deal with immunes. That and teleport away from immune trash, lol.
Yeah, what Rel said is pretty much the staple. I've seen some people run with Act 2 Defiance (defense aura) merc as well. Just work towards arming them with one of these in a polearm:
Insight is the rune word 'RalTirTalSol' for polearms or staves in Diablo II: Lord of Destruction or also in missile weapons in Diablo II: Resurrected. Insight is popular among casters due to the relatively cheap runes necessary for its creation, along with the Meditation aura it provides...