Yes, for two reasons:
- The AI can't handle dealing with two people, dropping the difficulty way down. If the boss got a bit of a boost to make up for it's poor targeting focus, or if it knew who to hone in on, it'd be much more reasonable.
- Who you summon is a total crapshoot. Sometimes you get a guy who runs right in and dies immediately, other times you get a guy (like me) who's working toward something and as such is geared to brutalize the boss in two or three hits. In DS2 I was working towards a spell you can only get by being summoned, so I'd be so over-leveled and overgeared that I'd pop in, do a bow, toss four lightning bolts at the fucker, and bow out. That couldn't be fun for the guy who summoned me, but I gotta get those sunlight medals, man.
All these games have are the bosses. They are the creative center-points, the memorable experiences. While I can absolutely understand summoning for something that's frustrating you, and will never look down on someone that does so, that sense of triumph will outweigh the frustration when you finally do it. If it doesn't, the Souls games might not be for you.
As it stands, the summoning mechanic has far too high a risk of ruining your fun.