out side of a mummy movie curses should not make you stronger...
if being turned to a drider is a curse then drider needs to be equal or less of a threat then drow...
If I can make an encounter with 2 Driders and make it a hard fight for 4 5th level characters, but average stat drow in 6-8 as a group is an Average encounter... I question the curse...
on the other hand if you say all Driders were powerful wizards and Warlords BEFORE... then it almost works... yea an average drow is CR 5, but one with 12 levels of wizard are a 16 CR... do getting down graded to a CR 7 or 8 is a curse....
Curses often provide some boon in exchange for a high price. And the fact that curses are more plot devices to make a moral point, the "price" is usually one that builds up over time or the bearer of the curse finds out is a lot harder to deal with than they thought.
Vampirism for example: eternal youth, heightened senses, increased strength, speed, resilience BUT you can never go out in the sun again, silver can kill you, garlic is poisonous, you can't enter a home uninvited, you can't cross running water more than 3 feet deep, and of course, the eternal hunger for blood (in some cases as limited as unbaptized virgins).
At first you seem to get a great deal of benefits, but then you start realizing how hard it really is to protect yourself from the sun, how rare it is to find an unbaptised virgin, avoid silver and garlic, and there's
always the hunger.
For a drider lets see:
You gain great strength, you gain new abilities (bite, spiderclimb, perhaps a stinger or webbing depending on the material), large size (and it's associated bennies and drawbacks), and assuming you don't lose your mind, a revered place in Drow society, however....
Large size has it's drawbacks (not so stealthy anymore), no lower half means no mortal pleasures, and you are essentially now in the "public eye" of drow society which just makes you a bigger target for all those murderous little ursurpers. You require custom armor (which may not matter depending on your wealth) and disguising yourself becomes incredibly difficult (but not impossible).
I'm not sure if driders get any sort of extended life, but elves are pretty long lived as it is.
The biggest point and of course the moral of many stories about curses-that-seem-like-blessings, is that in the short run, it's a big gain, but in the long run the curse is indeed a burden.
Not that one couldn't come up with some severe handicap for the driders, but such a handicap hasn't traditionally existed. And we all know how the 5e team feels about D&D tradition...
I disagree, I think the handicaps have always been there, they just more socio-political than mechanical, which are harder to express in games that aren't running a by-the-book Drow society.
Of course if you're running the sort of game that allows player Driders, Vampires and Werewolves, I doubt you're much concerned with the penalties. Such games can be quite fun, but they have a very, very niche place in D&D gaming.
There's a spell in one of the Forgotten Realms 3e books. I think it's FRCS, and it's in the Drow domain. You cast it on an ally and they get +4 Strength/Dex/Con and spider climb, plus all the drider penalties: large size (with undersized weapons) and, uh, yeah, that's it.
The Drow of the Underdark book has the spell "Dridershape" http://dndtools.eu/spells/drow-of-the-underdark--93/dridershape--1127/
