imho adapting to the new jungle is the real problem here (i had the same, especially after 1 year lol break^^). I did tons of bot games (with almost all heroes I have) just to draw myself a picture of the new jungle and how to handle the first clear/minutes.
My conclusion is, that many heroes who are used to full clear on their first run can't accomplish this anymore at all or only with sacrifices (jungle optimized masteries without mastery keystone). Hecarim is one of them. So what to can/should you make out of it as Hecarim?
a) you can go 12/6/12 - attackspeed marks - armor seal - MR glyph - Lifesteal Quints
http://gameinfo.euw.leagueoflegends.com/en/game-info/summoners/masteries/#HnDPypVao.3ZNwanqDV.2HXESg00
this will enable you a fullclear and leave you after the Rift Scuttler with enough HP & MP left for one gank attempt
b) go for a more fitting mastery and runepage build for Hecarim and don't full clear in the first run. Which mean a lvl 3 gank attempt after 3 jungle camps.
Imho this should be the more valuable way, cause Hecarim can gain so much power from the new mastery keystones.
Imho one you get the hang how to get the first minutes going, Hecarim should be a Nightmare in the hands of a good player with the new meta. It's just the start where he is risky (a bit like lee sin, but you are more gank addicted since of bad early clear).
What the new meta has for Hecarim:
- Stormraider's Surge if you want the free DPS burst along with the movementspeed <3
- Windspeakers Blessing and Runic Armor if you want to get really tanky in teamfights.
Further I rarely see Hecarim players build Zz'Rot Portal, which is an insanely good item imho for him. Gives him the defensive stats needed to initiate teamfights (armor + MR). Further the Point Runner passive makes his lane ganks more deadly, allows even safer splittpushing and escaping when his charge is on CD. In the enemy base it gets really funny for Hecarim with his passive in the endgame.
Pls don't give him up, just because his early clear is bad and his early play is risky. Imho it is worth when you see how badass he can be now in endgame. I would really like to see more pro play Hecarim. I just think he is underrated and played my to many noobs who just fail at him, because of his high skillcap.