Hey there!
So sometimes forcing an archetype can really come back to bite you in the ass. I usually don't decide what I'm going (unless I have a specific hero that comps well with specific archetypes) until after I receive the quest at hand. The shop will tend to offer you more of one type of minion than the other and it's important to capitalize on that.
Example: I had Chenvaala, which normally means that you would go elementals but ended up going Naga instead because of my quest and just capitalized on getting to tier 6 via elementals then went Naga.
Just play what's given to you and do your best to try and not force a specific strategy and your survivability will increase.
As far as the dude getting turn 12 golden beasts, it may have just fallen into his lap
Link in my signature for more discussion if interested
