So instead of 再度感じるくらいなら 死んだほうがマ use 再度感じるなら（むしろ）死んだほうがマジ
I feel like if you understood the grammar くらいなら properly, you would not be asking this question, so let me explain it so you can understand how to interpret it correctly in the first place.
くらい comes from the noun 位 which, if we look it up in a dictionary, originally comes from 座に居る (座居 / くらい), which should mean 座る所に座る in modern Japanese. And from the examples we can see that a common word used to explain all the meanings is 位置 (position, place).
This meaning hasn't changed much through history, and we can directly witness it with examples like 1位 (first place). For some reasons, people like to explain it differently when it is used as a particle. But the fact that it became a particle does not mean that the meaning has changed.
Now if we translate the くらい from the example sentences by "position" or "place", obviously it would not make much sense in English, but this is not about translation, you rather want to get the logic behind it, and by seeing くらい just like the positions in a ranking list:
You should have no problem understanding it in whatever situation it's used in.
For example, let's take the following example sentence:
「位」 indicates the position/rank/place on a scale where the "thing" (which we do not know about in this sentence) is 目に見えない (not visible), and the whole expression 目に見えない位 can be seen as an adverb the same way as an adjective like すごく is used as an adverb in すごく小さい.
Anyway, I don't think you need an explanation for なら, so let's take a look at your sentence directly:
What I've been saying until now applies to this sentence as well: If (なら) place (くらい) where I feel it again (再度感じる), the part/side (ほう) where I died (死んだ) is better (マシ) → If place where I feel it again, the part where I died is better.
Just looking at this sentence, we instantly know it's the singular form of the first person. However, if we take out the くらい:
It kinda feels like the 再度感じるなら is about someone else (the interlocutor) because of the 感じる, whereas the 死んだほうがマシだ is about yourself (= if you feel it again, I'd rather die). So although it's grammatically correct, I feel like it's (semantically) a bit unnatural in this specific sentence (at least without context).
So let's look at another sentence from Weblio:
金を出すくらいならたくさん出せ。 = If place where you give money, give much = If you're going to give money at all, give much.
Here if we take out the くらい, we can see that it is perfectly fine:
金を出すならたくさん出せ。 = If give money, give much = If you're going to give money, give much.
I think the translations say it all, so to answer your question:
Can なら be used as “rather than do…” by itself, without くらい？
Firstly, what gives this "rather than..." nuance to your sentence is the ...たほうが... and not the くらい, so your question doesn't really make much sense.
Otherwise, yes なら can be used without くらい in some sentences, but as we've seen the meaning changes.