The first thing to do to improve the capture quality is obviously change the capture card... it must not be a super expensive one; I suggest to avoid USB based (I have one and is really awful); an old and/or used PCI card, that would top quality some years ago, could be a good choice - it will be really cheap nowadays!
Mine is based on the Philips SAA 713x cheapset (could be SAA 7130, 7133, 7134... the bigger the last digit, the better) and it's pretty good.
Anyone consider the laserdisc internal comb filter really basic, compared to today's standard; it can be true, but as many capture card cheapset are old too, sometimes using a s-video out from a laserdisc is not a bad idea, in particular if you use a high quality player - that could have a better comb filter than your capture card.
A simple test is this: capture some footage and let the laserdisc display the time on screen; then look at the digits on the screen; if there are visible rainbow artifacts, the comb filter is not that good...
About the lasedisc players: the first one (CLD-HF9G) is really good, could be included in the top twenty (maybe to ten) laserdisc players of every time; the others are medium quality. If you decide to use the TOOT (two out of three) avisynth plugin, use the HF9G capture as first clip, as it will be the best.