Protective Spirit is not as useful if at all in Snowman layer since most folk will have ~500 health or more and almost all packets of damage are 50 or below Its the shear quantity of hits that kill folk, So yes SoA is good or any skill that blocks there normal attacks or reduces damage directly comes in handy the union spirit also helps somewhat in this dungeon.
As a warrior you could bring whirling along and heroes with splinter weapon, when they ball up which Im sure you know is quite often using whirling can be quite fun lol just get used to pre casting SoA on you before you take the initial agro also taking 2 copies of SoA helps.
As others have said there is no real point going solo for this dungeon since the only gain would be a slightly better drop rate, since the foes give no xp and you get the same number of points if you were with a full party.
Edit: Just to add a Panic mes makes the snowmen stupidly easy since they are so tightly balled normally and there snowball skill is a spell makes for a lot of interupted snowmen lol. Hope this helps.
Edit 2: As a warrior you have no real options to block there spells so no way of soloing the dungeon either, for example you will be kded and dazed a lot in the later mobs. Also VwK would not heal you enough to cancel out the 50 damage from snowball.
