While I can see some reason in cutting
Larder Zombie, cutting my ramp options, and especially one that works with
Havengul Lich, is not so great an idea.
Vesper Ghoul's going nowhere for anything but another highly flexible ramp option. At the moment I've been looking at
Rotten Reunion and
Swan Song as potential cuts for Wash Away, but
Larder Zombie is in consideration now too.
Urborg, Tomb of Yawgmoth would be somewhat nice, yes, but it is well outside the budget. There's also almost no synergy to that card and this deck as is. That budget issue's the same reason
Unholy Grotto is still sitting on the Maybeboard. The few things in this deck over the $10 limit are ones I had already, or caught at or before hitting that limit.
Zombie Master is similarly overbudget, though not so much so that it would necessarily be difficult to find a copy low enough in quality to drop below that due to age. The bigger issue is the threat it poses to me. Unlike most Lords,
Zombie Master is not limited to just helping you. If anyone else is running Zombies, which let's get real is pretty common due to the tribe's popularity, that leaves me open to them. Flying, Menace, and to an extent Deathtouch are all more reliable methods of evasion in this deck that don't depend on what lands my opponents have or that I buy and pull out one specific land.
Zombie Trailblazer, even ignoring the Swampwalk and Ashaya killing utility, also allows me to more safely attack into someone with open mana by using a few zombies that couldn't or shouldn't attack that turn anyway and
disrupt the mana supply before combat.