Just because a champion is listed as a 'bad teammate', does not always mean that the champion itself is bad (that COULD be a reason, but whatever). They may simply not contribute as much as other potential teammates to Hecarim's abilities.
Hecarim is not an especially niche champion requiring a team to revolve around his presence, but some champions synergize better than others with him.
General Teamfighting Partners:
These champions all have a lot of area of effect damage, which gives you absurd amounts of healing on
. Their burst or sustained area of effect damage all heal you buy 30% of the damage dealt, unlike the reduced amount of healing usually applied to spell vamp on area of effect spells.
Notice that a lot of these champions are AP mid casters. A lot of good teammates here will overlap with some of the mid mages.
These champions have typically reliable crowd control before and after 6, allowing you to gank for them easily both pre and post level 6.
These mages can enable an easy gank at level 6 with their respective ultimates. Before that, however, ganking for these mages will be a little harder.
These mages possess the ability to control the battlefield with their abilities, creating zones where the enemy does not want to enter.
Heimerdinger has nearly impossible to land crowd control and a bunch of abilities that play towards pushing the lane. He also lends very little to an initiation composition - he's better suited to a team that prefers to be initiated on.
He will be under the enemy tower regardless of how he plays. Also, he likes to take your jungle for additional money during his downtime.
These champions enable ganks on their lane very easily with their crowd control and damage, and/or can follow your initation with their own methods of aiding in the teamfights to great effect.
Their level 6 will essentially mean you are almost guaranteed to kill their lane opponent if you gank.
in particular can assist in a gank you are initiating on the other side of the map.
These champions are all helpful at letting you live through teamfights, sustaining off of their damage with
, chaining crowd control, or just outright saving you (
Fiora cannot help your ganks at all except with pure damage.
can give you some health back, but that's not a good enough reason to pick Fiora as a partner.
Much like Fiora, Garen cannot assist your gank in any way besides damage. It doesn't mean you shouldn't gank his lane early, because if he gets in range he will basically provide all the damage required for a kill, but be aware that he won't be doing any enabling for you without summoner spells.
Mordekaiser makes his second appearance here, as he can also go top lane. Not as bad as mid, because you can just let him farm the top lane and devote your attention to dragon and the other lanes, but it's still basically impossible to gank for him unless the enemy laner is dumb.
These supports can help your AD and you secure the kill on the enemy.
AD carries with crowd control are quite valuable, even if most of it comes at level 6. The others only really contribute with damage.
The following can follow up your initiation with their own crowd control and lock down the enemy for a fairly long time.
Area of effect damage, as usual, is a wonderful followup on an initiation. AD carries that can contribute that along with their autoattacks are an excellent choice, along with those with initiation ability (Ashe's
Basically puts you a man down when it comes to crowd control and damage.
Contribute less than the other AD champions, but are still workable.