"disproportionate emphasis" is a correct and usable phrase in written English.
It is typically used to refer to something, either a person or an object, that has been given too much emphasis in comparison to its importance or relevance. For example, "The teacher placed a disproportionate emphasis on the spelling test, causing the students to become anxious and frustrated."
At times this theme can have disproportionate emphasis.
There's a disproportionate emphasis in the British media towards leaving.
Will your newspaper's disproportionate emphasis on his minor sexual affair and unsurprising denial never end?
"The report's political framing and disproportionate emphasis on Labour risks undermining the positive and welcome recommendations made in it.
This has been a challenging series for opening batsmen, with the disproportionate emphasis on the new ball.
Corbyn said the report by the cross-party home affairs select committee was biased and had "a disproportionate emphasis on Labour".
The four-strong Olympic Qualification Standards (OQS) panel, which included Team GB chiefs Andy Hunt and Sir Clive Woodward, ruled that GB Taekwondo had placed a "disproportionate amount of emphasis" on certain selection criteria when nominating Muhammad.
Besides, there is little statistical evidence to support an active correlation between corporate tax rates and job creation, and so the emphasis on this is disproportionate.
Smaller factions within both major parties, though with greater emphasis on your side, command disproportionate influence while expressing little interest in bridging these divides.
Excessive emphasis on impact may give disproportionate rewards to those who evaluate interventions discovered by others and bring them to market, without giving full recognition to basic researchers, who invent and bring new interventions to clinical evaluation.
This was done given the recent emphasis on hospital disaster planning and the disproportionate morbidity and mortality that pregnant women have suffered in previous influenza pandemics.
