Fate/Grand Order - Are you my Master?

[Red Fel]

As d'Eon was my first 4 stars (on my first free roll too to boot), I'm biased towards them. They've accompanied me as my main servant, even more than Mash did, by tanking like a boss (as I said earlier, three turns of invincibility kicks ass). But that was when I started playing about two months ago, and I was doing the campaigns at a fairly low level. For a high level player with lots of high level servants, they may not be that useful of an addition to an existing team.
Objectively, if you have no need for a main tank, you should choose a more universally useful servant, I think.

I mean, my usual strategy involves using Mash as main tank, frankly. Combining her on-command Invincibility with her Taunt got me through the worst of Ibaraki. And Mash has additional party buffs, and is free, to boot. Sure, having her and another tank to take the heat off of Heracles might be nice, but it would also dramatically reduce my damage output. Or increase my party cost.

When it comes to "universally useful," though, there's the rub. Because out of all of these freebies, the only ones I don't have are Sumanai and d'Eon, Marie, Tamamog, and Liz. Tamamog is the closest thing to "universal," because Berserker, but I have Heracles for that, and he can go offroad. I don't know that I'd classify any of them as "universally useful."

I suppose I could just grab one to fill out the roster. Or grab one for the Interlude SQ - Marie and Siegfried both get two Interludes that drop SQ, everyone else only gets one SQ from Interludes. Or I could check which ones get bonuses in upcoming events... Hmm...

EDIT: So I decided to do some research. Here are several upcoming events, and which Servants from this freebie batch get bonuses:

• Onigashima: EMIYA
• Prisma Causeway: d'Eon, Elizabeth, Marie, Martha, Carmilla, Stheno, Tamamog
• Christmas Re-Run: Marie, Martha
• Christmas: EMIYA

So, not a lot of events that I could see for the rest of the year involving Servant-based bonuses. EMIYA is always a safe choice, as apparently are Marie and Martha.

I might end up going with Marie, then, just for the SQ and bonuses. Huh.