卒業論文より大変そうだよ sounds very natural, but it means like "It looks more difficult than the graduation thesis that I wrote". If I say "a graduation thesis sounds more difficult (than my homework)" in Japanese, it would be 卒業論文ってかなり大変みたいだね.
so 卒業論文より大変そうだよ makes it sound like i'm also writing a graduation thesis?
sorry.. i'm still confused. can i give you the full context? My friend and I were talking about our homework and he said 大変そうだな when i told him my homework. but then i wanted to say "your graduation thesis sounds more difficult (than my homework)" so i guess something like this: 私の宿題よりAさんの卒業論文はもっと大変そうだね。but i wanted to shorten it to 卒業論文より大変そうだよ. does it still hold the same meaning?
"your graduation thesis sounds more difficult (than my homework)" →(あなたの）卒業論文の方が大変そう is common, but you could also say 卒業論文の方がより大変そう. You have to add の方が after 卒業論文, in this case. 卒業論文より makes us feel "than a graduation thesis" in this case.
How to use より I can run faster than he. → 私は彼より(も）速く走れます。/私の方が彼より(も）速く走れます/ →彼より速いよ。/ 私の方が速いよ My sister is more beautiful than I. → 私より姉の方が綺麗です。/姉は私より綺麗です / 姉の方が綺麗です。 He loves me more than he loves you. → 彼はあなたより私のことを愛してるのよ。→私の方が愛されてるのよ。