As, I really like ANT though. Hoping to build one soon. Well, I assume you're talking about Mindbreak Trap. I don't think I'd sideboard it just to deal with ANT. In Vintage, it might be all-around useful enough to maindeck in some cases. And in Legacy maybe it will be useful enough as a sideboard card, but in Legacy, if it's ANT you're worried about, you should have a deck that can deal with ANT on its own, rather than relying on a one-shot sideboard card. Also, I assume the idea is that one can let Ad Nauseam go off, then stop the Tendrils with Trap. What if the ANT player draws into multiple Pacts off Ad Nauseam? That strikes me as too big a risk to wait around.
Comparing that to Crypt or Relic or whatever your favorite graveyard hate card is, even though Ichorid isn't as strong as ANT, those cards can pretty much always strike a serious blow against any graveyard reliant deck. Ichorid is one, but there's also Survival, Bomberman, Cephalid Breakfast, Threshold, and Loam. Especially those last two, which are huge. If Entomb makes a single deck particularly stronger, I think it would probably be Ichorid though. But my concern is that the stronger any of these decks get, whether it's Entomb for Ichorid or some new tech bringing Survival to the forefront, the presence of increased graveyard hate, even if the big decks deal with it (and Ichorid really has to be able to in order to be playable), is bad news for rogue decks that are trying to break in. In my case, I'm thinking of Pattern Combo. In your case, it appears to be Reanimator...