I personally think Mono Skeelz is very good in ELO, when SOA clans are almost everywhere. Yes they might be a bit weak to attack manipulation clan, but thanks to the addition of Dr Falkenstein, I have beaten strong draws of attack manipulation clan MANY TIMES. You can shortly find their amazing round-winning power and scary abilities like Greem and Snowflake etc very useful in ELO.
They do have weakness, but I don't think they are the attack-manipulation clans. From my experience, I always feel difficulty when facing Jungo (Super strong ability and scary bonus) and sometimes All Star. Just my two cents.