Originally Posted by emidln
The thing is, your 4-of answer trades 1 for 4 with theirs. How do you figure it would only come in around 16% of your sideboard games? I'd board it anytime the opposing deck can't board out enough creature hate. The only decks that the Confidant/Swarm/Defense Grid plan is good against are Control decks. (Your plan with Iggy Pop is to make Threshold a control deck (with terrible options) whether it wants to be control or not.) Control decks include Threshold, Tog, Landstill, U/x Variants, Stax, and other decks whose kill condition is way too slow for you to care about anything other than a double-tendrils while playing around Chalices/countermagic.
Also, you can get a needle 45% of the time by your first draw. This balances by the fact that your opponent will only have Crypt 40% of the time by this point. You then have 4-5 ways to find a Needle if you need it on top of that.
A semi-lethal Tendrils might (probably will) buy you a turn, but probably not two unless the Goblins player is having bad draws. That means you have to refill AND win next turn. How is that a viable solution?