Palace went 1-0 down in the first half when Nathan Delfouneso converted Tom Ince's cross, but Holloway, who managed the Seasiders for three-and-a-half years, rallied his troops at the break.
Owen Garvan equalised with a header and Glenn Murray's 18th of season put the host ahead, but Dicko had the final say, making it 2-2 in the last minute by turning home a Wes Thomas cross.
The result left Palace three points adrift of leader Cardiff City, which beat Blackburn Rovers 4-1 the previous night.
Leicester City dropped to fifth in the table after needing a last-minute equaliser from Jamie Vardy to earn a 2-2 draw at home to struggler Barnsley.
The Tykes arrived at the King Power Stadium without a win in nine and went behind thanks to Anthony Knockaert's goal, but put themselves on course for a shock win when Stephen Dawson and Reuben Noble-Lazarus found the net.
The travelling fans were ready to toast victory, but Vardy turned home David Nugent's pass with 17 seconds of the game left to steal a point for the host.
Middlesbrough took advantage of Leicester's slip-up as it moved up to third with a nervy 3-2 win at Peterborough United.
Faris Haroun gave Boro a two-goal cushion, before Dwight Gayle put Peterborough back in the game just before half-time.
Gayle then gave the bottom side a surprise second, but Ishmael Miller came to the rescue by grabbing the visitor's winner 14 minutes from time.
Republic of Ireland internationals Robbie Brady and David Meyler both scored their first goals for Hull City as the Tigers defeated in-form Watford 2-1 at Vicarage Road, where Troy Deeney grabbed a last-minute consolation for the host.
Kazenga Lua Lua stepped off the bench and earned fellow play-off hopeful Brighton & Hove Albion a valuable point in a four-goal thriller at Charlton Athletic.
Bradley Pritchard put the Addicks 2-1 up after Craig Mackail-Smith equalised Lawrie Wilson's opener, but Lua Lua struck 15 minutes from time to make it 2-2.
Nottingham Forest leapfrogged local rival Derby County in to ninth with a 2-0 home win over Burnley thanks to goals from Dexter Blackstock and Billy Sharp.
At the other end of the table, Albert Adomah's 25-yard screamer condemned Sheffield Wednesday to its seventh straight loss as Bristol City secured a 3-2 win at Hillsborough.
Gary Madine thought he had set Wednesday on course for a much-needed win when he put the host 2-1 up after Sam Baldock's strike had cancelled out Miguel Llera's opener, but the Owls striker then handled in his own box and Baldock made it 2-2 from the spot.
City, which started just one place above the Owls in the table, then stole all three points with Adomah's stunning set-piece that will pile more pressure on Wednesday boss Dave Jones.
James Vaughan struck four minutes from time to deny Bolton Wanderers victory at Huddersfield Town.
Zat Knight put the Terriers ahead with an own goal, but Bolton hit back through Kevin Davies and Chris Eagles.
Eagles then missed a chance to put the game to bed from the penalty spot and Vaughan made him pay by finishing Alan Lee's cross to make it 2-2.
DJ Campbell scored twice and Daryl Murphy was also on target as Mick McCarthy's Ipswich Town won 3-0 against his former team Millwall at Portman Road, while Derby County beat Leeds United 3-1 in the day's early kick-off.
Defender Jake Buxton deflected home a shot from fellow defender Richard Keogh in the 66th minute with the score at 1-1 and the Rams withstood a late barrage before substitute Ben Davies finished superbly on the break in the fourth minute of time added on.
Leeds midfielder Paul Green had cancelled out Conor Sammon's 15th-minute opener for Derby on the stroke of half-time.
Wolverhampton Wanderers edged past midlands neighbour Birmingham City 1-0 at Molineux.
Wolves was winless in six in front of its own fans going into the derby clash, a run stretching back to the start of September, while it had lost its last two on home soil.
But that sorry streak came to an end courtesy of Marlon King's 34th-minute own goal, the Birmingham striker slicing past Jack Butland when attempting to clear Bakary Sako's drilled free-kick at the front post.