JonnyP71
Explorer
It is. THe older abilty was an outright 50% magic resistance to magic though. SOme spells do not have saves and being immune to magic half the time is still better than advantage on saves.
And no sane DM allowed a Paladin in their campaign to have a Holy Avenger until they were very high level and it was approaching the time to retire the character off!!! (source - 10 years of DMing 1st edition - and I made that mistake once!)
How much experience do you have of running 5E?
PCs are surprisingly powerful and resilient after they have survived the 1st couple of levels - they are capable of dealing with a lot more than a new DM would reasonably expect, even without access to magical weaponry.