Have other Gush pilots found the [DPS vs. Mentor Gush] matchup difficult? I'm curious...
From the results we've read online, and the testing I've done with DPS vs. UWR Mentor Gush it has been about a 50/50 matchup, depending on deck configuration. The more Defense Grids you play main deck the better the match gets for DPS, as it invalidates a lot of the soft counters that Mentor and Gush decks rely on. Things like Xantid Swarm, Thoughtseize (takes opposing hatebears, TKS, and never misses usually make it worth the life), City of Solitude, and even Mind Twist (doesn't get Misstepped, and is better against more decks) are also very good tools for DPS and Gush Storm decks at the moment.
I split my two matches against White Eldrazi (punting one of them) - Adding Mystical Tutor and Balance to complement the Walkers and Swords is pretty strong. Mindbreak Trap also can do work against their most broken openers. Alternatively, JVP is quite good if you can get him active, Baleful Strix is quite strong against them. Gush can definitely be built to beat Eldrazi and the Gush decks that did well made the necessary adjustments. That doesn't mean that Eldrazi is not a powerful deck - it certainly is.
Jaco's version is likely much weaker against Mentor. The reason White Eldrazi has a strong Mentor matchup is the combination of Spheres and the big threats. Without the Spheres, Mentor can just go nuts and the deck is more susceptible to Supreme Verdict, which commonly sees play out of Mentor SBs.
To give you some tiny data, I went 2-0 (4-1 in games) against UWR Mentor Gush (both having a small Bomberman package) at NYSE4 with Unpowered Eldrazi, and thought the match was generally in my favor against Gush decks of all varieties heading in to this tournament after having tested the past few months (which is why I simply couldn't justify playing 4C Mentor at NYSE4, which was my other deck sleeved up and ready to register). Null Rod and 8 Wasteland effects function similarly to 8+ Sphere effects. Balance can be very good against Eldrazi, but often comes priced in with losing most of your hand when casting it against an Eldrazi player who usually has 1-2 cards in hand. I believe I had my board reset by Balance, Engineered Explosives, and Toxic Deluge at NYSE4, and it didn't even seem to matter in any of the games. Eldrazi Mimic plus one other resolved follow up threat is usually enough to finish off your opponent in those situations because of the damage already incurred before a sweeper is cast. I remember beating Oath in a fun G3 after he resolved Deluge to wipe the board, then I cast an uncounterable Mimic and passed, and then I cast another large (non-Reality Smasher) creature the next turn, triggering Mimic, and the game was over.
The main path to victory for Mentor from every playtest game I had was if the Mentor decks get a very fast start against any form of Eldrazi (ie. resolving a Mentor before Eldrazi or Workshop deck does anything relevant), but barring that they are usually on the back foot most of the game against the versions with 4 Cavern of Souls, as there is effectively zero working countermagic at that point, and even having 4 Swords to Plowshares is not usually enough to save you. Dark Confidant, JVP, and Young Pyromancer are all OK, but none really seemed to swing games like a turn 1-2 Mentor racing. The fact that dedicated Eldrazi decks are basically half creatures, and keep pumping out larger creatures makes it very winnable for both Tribal Eldrazi and White Eldrazi. Endbringer or Eldrazi Displacer can clean up the battlefield very quickly against Mentor if the board is clogged. This also ignores the ability for any deck to play Dismember, which matters more than you'd think.
Mentor certainly can (and will) adapt to the results of the last month, but I think the other decks will keep adapting as well. I know I will (both with Eldrazi, and all of my other decks). I have read consternation about Gush (and Workshop) decks occupying a certain varying percentage of the metagame, but I can honestly say this is the most open Vintage has been to me since like 2002-2004, if people will take the time and put forward the effort to innovate, and I'm way more excited to play Vintage now than anytime in the past few years. We all know Monastery Mentor and Gush are synergistic and the best of breed/most efficient at what they individually do, but there are Thirst, Gifts, Landstill, and other combo decks out there that can be competitive in this metagame, and you just have to put the work in to tuning them. I had a blast at this tournament playing, meeting new people, and chatting up friends of yesteryear. The post-tournament meal was my highlight of the weekend, and I wish we could have had time for more of those. NYSE continues to be my favorite tournament each year, and I'm thankful for all of the hard work @Prospero and crew put in. I really look forward to seeing everybody that can make it to Eternal Weekend in Columbus this year.