Though Quilled Greatwurm may be less impactful if its controller has no good attacks on the turn it is played, a 7/7 with trample with significant upside can still turn a losing battle into a worthy skirmish
Each time it attacks, you make more zombies
But with this lovely little green card, you can save anything, even lands like Field of the Dead
Generally I view Bargain as more of the combo or big control card with Necro being better for agro or disruption decks
Most interestingly, the activated ability on Hauntwoods Shrieker allows you to flip face-down cards up for free, even your opponents' if you want to maybe because its a bad card, or to make them lose the flip-up trigger timing
As long as many of your permanents are mana value 3 or less, you can always have something to return to the battlefield when Sun Titan attacks or ETBs