I think including Phyrexian Dragon Engine without Mishra would be like including only one half of a known combo -- when a drafter opens pack 1 by picking Kiki-Jiki, they do so expecting that the cube will contain other combo pieces like Pestermite and Exarch. For years I thought about cutting Hanweir Battlements for being underpowered, but I worried it would be false advertising for drafters to pick Hanweir Garrison then spend the whole draft keeping an eye out for a Battlements that isn't even in the cube (in the end, I cut both parts of the Hanweir package at the same time).
I dunno, those are pretty different scenarios. Twin and Kikki are pretty bad cards without the combo, and there's an extremely known combo with them that players expect to see. Conversely, the Garrison is a good card on its own, and you'd play it in lots of decks you wouldn't bother with the battlement in. I've run it for years and never had any complaints.
The problem is you really need to treat this as a red 3-drop (in a deck that can't get the unearth value this card is extremely sub-par as it dies to every damage, murder, and shatter effect in cube) and red 3-drops are so stacked. The unearth is a really good post-wrath turn in aggro though - you dome them for 4 and get to draw 3. Leaning towards not testing at 465, but could be convinced.
I dunno, those are pretty different scenarios. Twin and Kikki are pretty bad cards without the combo, and there's an extremely known combo with them that players expect to see. Conversely, the Garrison is a good card on its own, and you'd play it in lots of decks you wouldn't bother with the battlement in. I've run it for years and never had any complaints.
375 unpowered cube - https://cubecobra.com/cube/list/601ac624832cdf1039947588
375 unpowered cube - https://cubecobra.com/cube/list/601ac624832cdf1039947588