I don't think we need actual spell tiers, but if the same spell simply looks more impressive every 15-20 levels or so (as in, it's the same spell down the line, but as the OP illustrated, the Fire spell's visual effects at level 1 vs level 20 would be drastically different), I'm all for that. No having to re-balance diddly squat, but gives more of a visual reason as to why the exact same spell is doing more damage down the line.
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