Interesting and thoughtful question!
Let's start with:
כָּל־אֵ֛לֶּה שִׁבְטֵ֥י יִשְׂרָאֵ֖ל שְׁנֵ֣ים עָשָׂ֑ר וְ֠זֹאת
אֲשֶׁר־דִּבֶּ֨ר לָהֶ֤ם אֲבִיהֶם֙ וַיְבָ֣רֶךְ אוֹתָ֔ם אִ֛ישׁ אֲשֶׁ֥ר
כְּבִרְכָת֖וֹ בֵּרַ֥ךְ אֹתָֽם׃
All these are the twelve tribes of Israel, and this is it that their
father spoke unto them and blessed them; every one according to his
blessing he blessed them.
"father" refers to Ya'akov (Jacob). Q? What do the bolded words really mean? Doesn't it seem superfluous to say "...according to his blessing"?
Or HaChaim on Genesis 49:28:1:
פי' הראוי לו כפי בחינת נשמתו וכפי מעשיו, כי יש לך לדעת כי הנפשות כל
אחת יש לה בחינת
המעלה יש שמעלתה כהונה ויש מלכות ויש כתר תורה ויש גבורה ויש עושר ויש
הצלחה, ונתכוין יעקב בנבואה לברך כל אחד כפי ברכתו הראוי לה המלך במלכות
והכהן בכהונה וכן על זה הדרך ולא הפך המסילות:
ברך אותם וג
. אמר אותם לשון רבים להיות כי ברכת כל אחד ואחד תועיל לעצמו
ולכל אחיו כמו שתאמר כשיברך למלך שידו בעורף אויביו הנה מגיע הטוב לכל
אחיו. וכן כשירבה מעלת אחד ושפעו והדרגתו לכל אחיו יגיעו גם כן מקצת דבר,
[I apologize that while my Hebrew is fairly good, there are some words that I can't accurately translate, here. Also, I'd rather summarize the essential points of the above, for purposes of my answer. I've pasted the entire text, in Hebrew, anyway.]
There are 2 aspects of Yaakov's blessings. The first is that he recognized that each of his sons had his own unique special leadership qualities that should remain independent. That's an essential part of that person's soul, and in terms of a tribe, each tribe has its own "soul". One son had the crown of Torah; another the crown of kingdom; another has bravery; another has riches; another has success. Thus, Ya'akov blessed each one according to his own, personal blessing, e.g. the king was blessed with kingdom, the Cohen with the blessing of Priesthood.
But, the end of the verse seems grammatically unparallel because it ends in אותם - them instead of אותו - him.
Summarizing the 2nd part of Or Hachaim commentary:
Ya'akov also blessed each person that his own unique qualities would influence and help each of the other tribes. For example, the one blessed with Kingship, should be a king and have influence on all the other tribes. (My comment - after all, you can only have one king, otherwise there is chaos!)
My own comments:
Despite the quarreling and bickering in the desert, we see that each of the tribes marched under their own flag and banner, and every was unified. During Joshua, even after the land was apportioned, there was, for the most part, tribal unity. During the days of the Judges, yes, things declined somewhat, but for the most part, there was tribal unity esp. when it came to battles. A few tribes didn't cooperate with Devorah and Barak. And, Binaymin was almost wiped away in their civil war against the other tribes - notable exceptions. Here's where we see unity despite separate tribes
On the reverse, special leaders emerged from various tribes. Shimshon from Dan; Barak from Re'uven, and of course, the 1st king, Saul, was from Binyamin, the smallest of the tribes in population (refer to what I stated that they were almost wiped out by the others!)
In summary, I think that the lesson learned is that while far from a a perfect system, Ya'akov knew what he was doing and what he meant in his blessing. At the end, you and I and all of us turned out OK ;-)