Oathbreaker controls undead as long as their level is less... this makes it a very strong class in act 2 but not as a muliclass and it also blocks you respecing
Druid is strong as a caster, melee or talker but it doesn't do range damage which is why a few Warlocks levels can help but Warlock wants to be good more than evil
the strongest class is Druid but Druid is also a class that needs skill i.e, if this is your first run i'd go for Warlock as that is simple to learn
if i did this build I'd start as Druid to get the base class and talking options at the grove, then I'd take a level in Pally to unlock amour and my 3rd - 7th levels in Warlock to have charisma as my main casting stat... if you want a more melee build i'd take 3rd level as Warlock then 4th -6th as druid to make quarterstaff hit as magic charisma instead of building for str
making a multiclass means you need all your different classes as soon as possible in the level order and the final one is the most important because thats your main stat... you end up with a weaker character at the end of act 3 because the 11th class tends to have the best bonus
