/fill clocks + /testfor commands causes a lot of lag

I made a map that uses a lot of commandblocks and fillclocks. The map is now in Beta and there are several Beta testers that are testing this map. One problem I found, was that the map really laggy is on servers. I suggested them to use more ram, but even 3gb of ram and 2-3 players online would have a lot of lagg. Recently Qmagnet(https://www.youtube.com/user/theqmagnet) said in his Diversity DevCom(https://www.youtube.com/watch?v=FpkCp8gbAt4) (Arround 09:09) that running testfor commands with a fillclock will cause a lot of lagg on multiplayer servers. And I don't think that's intended. I think it has to do with the /testfor command being slow, and that it can't finish before having to run again. So I think this is the thing that causes lagg on my map. I really need this getting fixed, cause my map is almost inpossible to play now(with all the lagg)(on multiplayer)(while it is a multiplayer map D: ).

Steps to reproduce:

On multiplayer:

1. Make a fill clock:

Commands:
Top: fill ~ ~-1 ~ ~ ~-1 ~10 redstone_block,
1 air block in between,
Bottom: fill ~ ~1 ~ ~ ~1 ~10 clay

Now place a redstone block in the middle and the clock will start running. To stop the thing, power the top command block.

2. Add a lot of /testfor commands to it.

Thanks for your time,

-JustRamon

PS: This map was made (and is being made) on a Realm. On the Realm we didn't have any lagg. I don't know if this is because that server has a lot of ram, or that those servers are magical

PS2: If you look at the screenshots you can see the commands, and the screenshots of the commandblocks. Almost all the commandblocks at the fillclock have testfor commands in them.