Welcome to the forum Nanase but would disagree based on two things
1) various Han loyalists like Xun Yu and Liu Yu lived longer then Sun Jian. Liu Yu was powerful if lacking miliatry competence. Ma Teng was not a Han loyalist, he rebelled against the Han.
2) I'm not convinced Sun Jian was a Han loyalist. All the things you mentioned (I'm assuming you don't know his his murder spree of Han governors?) more point to me a man taking advantage of the chance to rise up the ranks.
When he did, he showed little respect for Zhang Wen. Sun Jian then advised Zhang Wen to execute Dong Zhuo, but Zhang Wen declined as Dong Zhuo held high reputation in the west.
While that is recorded in the SGZ and the ZZTJ, some historians do dispute whether that was Wu propaganda rather then truthful.
Hearing that a mass army had arrived, the rebels promptly surrendered. When Zhang Wen and the rest returned to the capital Luoyang, however, the court held that the army did not engage the enemy and thus no honor was accorded.
Zhang Wen and co failed, despite the brilliance of Dong Zhuo and Sun Jian, the rebels suffered one or two defeats but the Han army also suffered loses and didn't get anywhere.
He scored a brilliant victory and killed the enemy commander-in-chief Hua Xiong in battle.(In Romance of the Three Kingdoms, Hua Xiong was said to be dramatically killed by Guan Yu.)
Hua Xiong was probably an administrative officer and he was rank was Chief controller.
Later, when Yuan Shu declared himself emperor, he held Sun Jian's wife Lady Wu hostage in exchange for the seal.
I believe that has also been heavily disputed by historians
(Which he took orders from his Han superior ,I wonder if only he refused it and built his powerbase around Wu instead of attacking Liu Biao with his army but he was dumb loyalist in my eyes)
I would suggest he did it becuase Sun Jian had no powerbase and Yuan Shu was his liege-lord, if Jian refused then Yuan Shu could just kill him.
“You, are a rebellious son who abandoned his father. You are a cruel brigand who murdered his lord. How can Heaven and Earth put up with you for long? And unless you die soon, how can you face the sight of men?”