spider is strong, if your enemies are noobs that is, any intellegient player will buy a set of wards and he will be useless for 3 x sentry_ward.duration(), if he gets wards himself then just run back and forth near your ward and the moment you see his ward kill it or FF the spider and see him die within a few seconds, if he gets gem then laugh urself out and kill him, it will just drop and byebye gold for buying a gem...
anyway, i have a few comments on 2 of the 4 new heroes...
nortrom - teh silenzah
this hero is kinda "imba," almost no agi and intel based hero will win against this him toe to toe, also, strength based heroes relying on some sort of direct damage wont win... naix will own him sure cause naix doesnt need spells except ulti... his ulti IS strong, silence for 2,4,6 seconds(am i correct, cant recall) for each hit of his attack which is RANGED, has healing wave, summons "downgraded" infernals, and has an starfall-like-aoe that has insane cooldown... given the right amount of items he can push, he can kill heroes with ease, he can defend the base and he can heal, no hero can do that...
teh oblivion
quite ok hero, his aura is kinda useless IMHO, reducing mana regen for all enemy heroes, but hey! he's an intel hero so going close to them means you are dead... @.@ his ultimate is kinda imba, 100/150/200 HP/sec life drain for 7 seconds with a cooldown of less than a minute IS strong... though unconfirmed because i have only used him once but i think that the "banish" like ability coupled with his lvl 3 ulti will deal around 280 damage for the 1st few seconds of his ulti (gonna check it out)... even the "anti-mage" was running from me... and his AOE, nether blast(?), is strong, lvl4 deals 350 damage to units (coupled with his banish ability gives a whopping 490 pts of damage) and 100 damage to structures with a nice cooldown...