Phantom Knights remain the deck to beat in this current format, withtheir high consistency, large tech space, access to Limit 3's, in-archetype Negate+Destroy, and OTK Potential.
In my opinion, I don't think Infernoid fits the bill as a sole Tier 2 (and frankly might have a shaky spot amongst Tier 3 decks). Its matchup against Phantom Knights is a coinflip at best and even then Phantom Knights can play through the average Infernoid opener with ease.
Additionally compared to other Tier 3 decks, primarily Mekk-Knights, it has a rough time, considering that list in particular has adopted a slower playstyle while also accessing the Loading... reliably. The Salamangreat matchup is mostly a coinflip, with whoever goes first being advantaged. D/D/D can also search Lancea with Loading... which spells trouble for Infernoid specifically.
When combined with the rather modest numbers in the past week, despite its inherent strengths across a pool of various decks (Going first with Infernoid is usually strong regardless), I could easily see Infernoid losing its Tier 2 spot in the upcoming weeks.
D/D/D has found its place in the meta. With Infernoid being prevalent in the meta as the main sack deck, D/D/D has found itself a good meta matchup. Having access to big bodies that are difficult to out for Infernoids and having a way to search either their starter OR Loading... (which has a huge impact in this current meta against multiple decks), it is no wonder that we've started seeing D/D/D achieve results in leagues and tournaments alike.
On pure representation alone one could easily argue Mekk-Knight moving up on the Tier List, as the deck has had a solid week of tournament play and conversion. However, the TPC have decided this overperforming of expectations will curb back down in the following week, but this notable performance should not be disregarded, as Mekk-Knights haven't lost too much with the recent format change.