I've been playing with houserules for awhile now. These 3 are now I think all you need.
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We started with 5 houserules, then also added unearthed arcana and adjusted them, then had like 30+ house rules and wrote all together in a huge document.. at some point it had 80+ pages.. (and caused more work than playtime) now we have our own system that is kind of compatible with d&d source books.. but yeah: it is worth it? Our whole system added much more realism, but that could have been achieved by staying on lvls 1-3 for the whole campaign too.