Rectors are indeed "rulers" of their parishes. As such, some are excellent, and some are substandard. The same is true for assisting clergy - whatever their designations.
Having adopted a secular "up the ladder" mentality, we tend to think of competent assistants as wanting "their own" parishes someday. In fact, we are likely to think less of a faithful assistant who has found a niche in which (s)he feels called to serve indefinitely. An exception would be assistants who are cathedral canons, especially at a prestigious cathedral; titled, they seem to be more acceptable.
An academic dean of a state college called into his office a faculty member with an excellent reputation for teaching. With a congratulatory tone, the dean informed the young professor that, if he would go through the required application process, a top-notch administrative position would be his. The puzzled teacher explained that he loved the classroom as well as research and had no inclination whatsoever to become an administrator. Dumfounded and irritated, the dean replied, "I don't understand you. Anybody who's any good wants to go "up" into administration."
The secular "up the ladder" attitude is truly a spiritual infection, whatever the field. Among clergy, the desperate need for a personal identity and recognition as a rector (of a large church) is similar to those scheming to wear the purple. Baptism has never really taken hold in the life of ecclesiastical climbers; for their sense of worth and purpose, for their very self-definition, they need to advance to the bigger and better, however each perceives vocational progress.
What ever happened to being called by the Spirit to serve - without regard for titles, prestige, shirt color, and job description? Why is our compensation tied to a secular model?
I knew a very holy priest in Connecticut, a man (now in the next life) truly committed to serving God as rector of the small parish to which he was called. He served faithfully and quietly. The bond of love between him and his flock was remarkable. The congregation he pastored was a genuine church - a people of God. He served on a diocesan committee now and then, not to improve his resume, but to serve in response to a call.
In Connecticut, Massachusetts, and New York I was privileged to know some faithful and effective clergy who were called as assistants and remained such until their retirements. They were extremely secure and unpretentious people, ambitious to serve God and God's people whether in congregations or diocesan commissions.
I do hope that at some time the Church will reassess the value of assistant ministers. After all, aren't we all (clergy and lay) supposed to be assistants to Jesus Christ?