the thing is different abyssian decks play very differently
abyssian is the most segregated faction as there isnt just one set of cards all decks play (except lure)
the one thing you need to learn above all else is positioning and counting more so for abyssian than any other faction
counting lethal from 15 wraithlings in awkward positions can be easy to miss
tips for swarm archetype
1: always count how many things can die if you have deathwatch in hand or on board. be very careful as there will be a lot of things on board if you are doing it right.
2: use your opponents turn to plan your moves (just in general, even more so with lots on the board)
3: keeping your swarm alive is important but so is staying within range to be able to cash it in. knowing when to switch between aggressive and defensive is key. baiting your opponent into walking towards your swarm is difficult, but your most likely win condition.
4: if your opponent is magmar, lyonar, songhai, or has a thunderhorn, your swarm WILL be answered one way or another no matter what you do. plan on it. if your opponent is one of those and has 5 mana get as much use/damage out of your swarm as you can before plasma storm, rebuke, tempest, flamewreath, ghost lightning, or any thunderhorn shenanigans(songhai/vet/vanar) can wipe your entire board.
5: never dump your entire hand unless you have lethal or no choice. the best way to counter point #4 is to always be able to recover after a board wipe. its good in the early game to swarm the board before they can get their aoe to clear your board and just win turn 2, but this can backfire and requires a god like opening hand
6: playing a bunch of minions around an empty space(against songhai,magmar,lyonar) or your general(against songhai,vanar,vetruvian) in the middle is very dangerous as every faction has a way to punish you for that by killing everything around that spot
7: always hold onto at least 1 win condition even if it doesnt seem useful right now. grimwar, soulshatter pact, furor chakram, even shadowdancer. without these, your swarm cant actually do enough to matter since swarm relies on the suprise factor so heavily. being able to cash in your swarm, no matter how meager is vital.
creep, dying wish, myth, aggro, and memes all play very differently (except maybe myth and wish can play the same. maybe)